mabriss lethe
2007-01-09, 08:12 PM
The Broken Path: An Alternative Magic system
There are dangers in working outside the rules of magic. But there is great power. Easy power. All it requires is a little less control. A little less finesse, and viola! A raging torrent of magic is at your disposal. All those useless exercises your master taught you were a total waste. Real power comes from giving in to the magic and riding it out. Sounds great right? Too good to be true? You know the saying about things that are too good to be true.
But, oh! That power! Maybe a little risk is worth it. It can't be that dangerous. If things look like they're getting out of hand you can always stop.
The Power...
Congratulations, you've just taken your first steps into temptation, your first steps on the Broken Path.
What is the Broken Path?
The Broken Path is an abomination to most master magicians. It's the easy way out that the less disciplined students find themselves drawn into. It's all the shortcuts and fudges lazy wizards and sorcerers are punished for using. But even after a student sets out on his own, those failed experiments and attendant punishments might sit in the back of his head, waiting to be used. The Broken Path is a place where desperate or power hungry magicians find themselves. It's power at the expense of control. True, the techniques of the broken path yield tremendous returns. Sometimes, though, you get a lot more than you bargained for. Sometimes the magic runs wild. It's unstable. The spells will come out twisted, reshaped in unpredictable ways. Summoned creatures can turn on their masters. Healing spells will leave grotesque scars. Fireballs can detonate late, or even worse, prematurely. Constant and long term use of these forbidden techniques will leave the caster little more than a raving lump of insensate flesh, assuming the power doesn't destroy him outright.
How Does it Work?
The caster invokes the power of the Broken Path by improperly casting a spell, then riding the wave of rogue sorcery released as a result. If the caster can latch onto that excess, some of it can be channeled into specific effects. If the caster loses control, though, the magic will latch onto this world, finding its own form using whatever template is nearest or most convenient to assume, usually the caster himself, in some form or another. The original technique was probably stumbled upon accidentally during a caster's apprenticeship, but once he's learned his art, walking the Broken Path must be a deliberate act. He has to intentionally break the discipline instilled into him. Initiates walking the Broken Path learn to walk on the edge of a blade, trying to gauge just how much power they can safely rechannel. After a while, casters become addicted to the rush of power, the feeling of gambling against the very forces of the universe. It's an adrenaline junkie's dream.
Thoughts on the Broken Path
This is the part I could use some feedback on. I know it sounds a lot like the wild mage of old, but that isn't the flavor I'm looking for. I want this form of magic to be risky and available to anyone foolish or desperate enough to try it. Sure, sometimes beneficial or at least relatively harmless fluff effects will accompany its use. But I want the players to feel like they're playing with fire when they use it, that they're potentially courting their own destruction when they call on this power. It definitely has the flavor of something an arcane caster (especially a spontaneous caster) would use, but I'm not sure I want to limit it to that. There's something appealing to me about a cleric drinking too deep of his god's power in a moment of desperation and things going horribly wrong. There are questions concerning aspects of it as it relates to spontaneous casting vs. prepared casting. I want it to be flexible and tempting for a player to use. If from time to time things seem overpowered, I want to find ways to balance it out by making it extremely dangerous to the caster to use. The Broken Path is all about breaking the rules and then suffering the consequences for it.
The Broken path is meant as a suppliment to the standard d20 magic system and shouldn't have too many bugs left in it.
It's sort of large and ungainly as it stands, so I've put everything behind a spoiler tag to help neaten it up a bit. (yes, I'm learning, I'm slowly learning)
Take a peek and let me know what you think. Most of the hard and fast numbers for DCs and such are by no means set in stone if you think it should be harsher or gentler on the casters, then just let me know.
Basic Mechanics:
Any character with a caster level of 1 and at least one rank in spellcraft or knowledge arcana can fall into the Broken Path. My reasoning: I want it to be accessible to pretty much every caster from the get-go. you won't get the full benefits this way, but it's more to make a chink in the character's armor, setting them up for an even greater fall in the end. A character with only the most basic understanding of the Broken Path can, when casting a spell, declare it to Broken. A Broken spell gains either a bonus of +1 caster level or +2 to the save DC (the player's choice). Ranged touch spells have a -1 penalty to hit, being, at best, clumsily cast endeavors. Now the player has to makes a wisdom check on a d20 versus a DC of {10+(2X spell level)}. (The skill Broken Path Sorcery can be applied here once it is learned.) A failure to meet the DC results in a Flawed spell. Flawed spells are different in some important way to the original. The details are left up to the DM but good examples include randomly changing the spell's energy descriptors, shortening the duration of the spell, strange and lingering side effects like uncomfortable rashes or the temporary growth of fine scales. Feel free to get brutally creative, but don't just drop damage anvils every time. That's what critical failures are for. When a player rolls a natural 1, the Broken spell unravels, blowing up in his face in the form of Backlash. When backlash is incurred, the spell is lost and the character takes some form of damage as rogue mystical energies rebound on him. Some benchmarks could be for the caster to take 1d6 damage per level of the spell cast, or taking a -2 penalty on the character's primary casting attribute per level of spell for 24 hours, Things like that. If you, as a DM come up with something along the vein of a creative curse to have the character labor under, then that works for me, too. It should take the form of some sort of serious smack down. If you decide to incorporate this, I recommend that you refrain from telling your players all the risks involved. Just give them a general idea as to what will happen when they use it. Tell them bad things could happen but don't be too specific. Let them figure the rest out on their own.
New Skill: Broken Path Sorcery (Wis)
Untrained: Yes
Retry: No
Special: Broken Path Sorcery is considered a Cross class skill to every class with spell casting abilities and prohibited to all other classes. It represents the ability to sense and channel unbridled magical energies. A character adds his ranks in this skill to the roll made when casting a spell with the Broken descriptor. Characters gain a +2 synergy bonus if they also have 5 ranks or more of the skill: spellcraft
New Feat: Broken Path Initiate(Broken Path)
Prerequisites: Ability to cast 1st level spells, One rank of Broken Path Sorcery, one rank of either spellcraft or Knowledge: arcana
This character has gained some hard won proficiency with casting Broken Path spells and knows a trick or two about how to avoid getting burned by it.
Benefit:The Skill, Broken Path Sorcery, becomes a class skill, and the character gains an extra 1st level spell as if gained through a high ability score. This spell can only be cast as a Broken spell.
New Feat: Broken Path Adept(Broken Path):
Prerequisites: Caster level 5th+, Broken Path Initiate, 8 ranks of BPS, 5 ranks of either spellcraft or knowledge arcana.
Benefit: The caster has become an adept of the Broken path, and as such, gains a +2 competence bonus to all Broken Path Sorcery Checks. In addition, The bonus given to broken path spells increases to +2 caster level or +4 to save DC, The character gains an additional spell of either 1st or 2nd level as an Initiate does.
New Feat: Broken Path Mastery
Prerequisites: Caster level 10th+, Broken Path Initiate and Adept feats, 12 ranks of BPS, 8 ranks of either spellcraft of Kn: arcana. Must have overcome Spellthirst
Benefit: A master of the Broken Path gains a +4 competence bonus to all Broken Path Sorcery Checks. This replaces the bonus from the Broken Path Adept feat. In addition The bonus to Broken path spells increase to +3 caster level or +6 to save DC. An additional bonus spell can be chosen from levels 1-3 following the same rules as before.
New Feat: Broken Spelltwist (Broken Path/Metamagic)
Prerequisites: Broken Path Initiate, Ability to cast 1st level spells, one rank BPS, one rank spellcraft or Kn: Arcana
Benefit: The character selects three Metamagic feats he already meets the requirements for. He can use the Broken Path to mimic them. Of the three, the player may only select one that has the requirement: "must know 2 other metamagic feats" Unless, of course, the character already possesses two other metamagic feats..then ignore this. Broken metamagic spells don't work in quite the same way as normal metamagic. Broken metamagic is applied the moment a spell is cast, whether that spell be spontaneous or prepared, and takes no real extra time to accomplish. Should it be incorporated when a spell is prepared, the caster must make a broken path sorcery check with a DC of 10(+ the number of hours since it was prepared). The spell is lost when the character fails the roll. Rolling a 1 indicates that 1d4 other spells chosen by the DM are lost as well. Spelltwist takes up a slot of the same level as the original spell, regardless of the spell level the original metamagic feat would call for. However, remember those extra spell levels. For every level the metamagic spell would otherwise occupy, The Broken Path DC increases by 2, as if it actually were taking up a spell slot of the higher level. Broken Path metamagic feats and normal metamagic feats cannot be applied to the same spell. The conflicting energies causes the spell to be lost and deals 1d4 damage to the caster per spell level. (this included the phantom levels applied by Spelltwist)
Spelltwist can be taken multiple times, each time selecting three new metamagic feats to mimic
New Feat: Blood from a Stone (broken path)
Prerequisites: Caster level 1st, One Rank Spellcraft or KN: arcana, one rank BPS, Con 13+, Ability to cast spell spontaneously
This character can, at a cost to his health, cast more spells than he'd usually be able to manage.
Benefit: The caster may take two points of constitution damage per spell level to cast a spell without using up a spell slot. This spell can be of any level known to the character as long as the resulting Con damage wouldn't drop the character's modifier below 0. 0 level spells count as 1/2 of a level for determining constitution damage. The character may cast in this fashion as long as he still retains a positive Con modifier. Once his modifier reaches 0 then he has exhausted this route. As a secondary drawback, Blood from a Stone causes a form of backlash that fills the caster's body with uncontrolled sorceries.This means the character cannot be healed magically until he naturally recovers all of his lost Con points.
New Feat: Shattered Chains (metamagic?/Broken path)
Prerequisites: Broken Path Adept, Broken Path initiate, Caster level 5th+, etc...
I don't know if this one should be considered metamagic or not.
The character can cannibalize existing spells, breaking them down into raw energy that can be directed as a crude, but potentially powerful weapon.
Benefit: Upon the successful attempt of a Broken Path Sorcery check, {DC = 10 plus (2x spell level) +2 },The caster tears the bonds containing his own uncast spells. The resulting blast can be directed in a quarter circle, dealing damage indiscriminately to all legitimate targets within a range of 10 feet (+5 feet per caster level) The damage done is equal to 1d6 X the sacrifices spell's level. The caster takes 1 point of damage per spell level as well. The damage has no energy descriptor. It's just raw, barely controlled power. A failed check resulting in a flawed spell sends the blast into a random direction. or adds some other random effect to the blast. (survivors gaining temporary damage resistance, something like that) A natural 1 detonates the power within the caster's body, causing them to take the full brunt of the damage. This replaces the normal effects of basic broken path sorcery (ie the bonus to caster level or Save DC)
The Pitfalls of the Broken Path:
Flawed spells: When a character fails a Broken Path Sorcery roll he creates a flawed spell. These spells still work, but never accomplishing the expected results. A Flawed spell is completely in the hands of the DM. Here are some suggested flaws. Energy descriptors can be exchanged in any spell that has them. Fireballs could instead to cold or sonic damage. Targets of damage spells could find themselves with a temporary immunity or resistance to some quality associated with or opposed to that magic. Someone hit with a fireball could be granted cold resistance or fire resistance. The DM can feel free to change the target of the spell or to have area spells hit in the wrong place/ direction. Healing spells, while fixing damage, might leave horrific scars or discolored birthmarks behind. Necromantic spells might accidentally raise fallen targets as uncontrollable undead. Summoned creatures might not obey the caster, attack him on sight, etc. A kinder gentler DM might just settle for strange lights accompanying the casting along with peculiar odors or screeching sounds. But that, in my honest and never humble opinion, just isn't all that much fun.
Backlash: When a character rolls a 1 on a BPS check, the spell is lost and the caster suffers backlash. simple backlash can take the form of 1d4 or 1d6 damage to hp per level of the spell attempted. You want it to hurt, potentially a lot, but maybe not kill them outright. Be willing to fudge a little especially early in the game when a first level wizard botches the roll and then gets hit with a 4....dead wizard. Other options could include 2 points of damage to a character's primary spellcasting attribute per spell level. Having some of the Flawed spell effects hit the caster during backlash can lead to interesting twists. You might also drop a curse of some sort on the character for a brief time. Backlash effects shouldn't last more than 24 hours, but if you find a good one that you think should be semipermanent, then go right ahead with it.
Spellthirst: Keep track of every time a caster receives backlash. Mark a little point on your notes or something. These magical energies begin to accumulate in the body. The only way to decrease backlash is to refrain from casting broken path magic. Backlash fades at a rate of one point per month until it's back at 0. Using the broken path at any time starts the clock back to the beginning of the month. As these magical energies slosh around, the caster becomes more and more dependant on them. It becomes an addiction. If at any time, the number of Backlash points exceeds the caster's highest ability modifier, then he acquires the curse of spellthirst. A character under the influence of spellthirst acts as if constantly fatigued unless he voluntarily sacrifices a spell every twenty four hours. A 0 level spell will assuage the spellthirst, but higher level spells give the character a temporary bonus to strength equal to the level of the spell sacrificed. This bonus fades quickly, lasting only 10 minutes (+1min per caster level) A spellthirsting character can sacrifice as many spells as he wishes per day.
The only known way to break a caster of spellthirst is for them to go cold turkey and not use magic of any sort for a month. This includes wearing or carrying magical items. The caster's body needs time to let all that accreted power work its way out. At this point, backlash goes down to one point below spellthirst levels and will decrease as normal following the rules above. Being targeted by magic doesn't have an effect on breaking spellthirst.
Playtesters are welcome, though if you use it, drop me a pm or something and give me a little feedback
There are dangers in working outside the rules of magic. But there is great power. Easy power. All it requires is a little less control. A little less finesse, and viola! A raging torrent of magic is at your disposal. All those useless exercises your master taught you were a total waste. Real power comes from giving in to the magic and riding it out. Sounds great right? Too good to be true? You know the saying about things that are too good to be true.
But, oh! That power! Maybe a little risk is worth it. It can't be that dangerous. If things look like they're getting out of hand you can always stop.
The Power...
Congratulations, you've just taken your first steps into temptation, your first steps on the Broken Path.
What is the Broken Path?
The Broken Path is an abomination to most master magicians. It's the easy way out that the less disciplined students find themselves drawn into. It's all the shortcuts and fudges lazy wizards and sorcerers are punished for using. But even after a student sets out on his own, those failed experiments and attendant punishments might sit in the back of his head, waiting to be used. The Broken Path is a place where desperate or power hungry magicians find themselves. It's power at the expense of control. True, the techniques of the broken path yield tremendous returns. Sometimes, though, you get a lot more than you bargained for. Sometimes the magic runs wild. It's unstable. The spells will come out twisted, reshaped in unpredictable ways. Summoned creatures can turn on their masters. Healing spells will leave grotesque scars. Fireballs can detonate late, or even worse, prematurely. Constant and long term use of these forbidden techniques will leave the caster little more than a raving lump of insensate flesh, assuming the power doesn't destroy him outright.
How Does it Work?
The caster invokes the power of the Broken Path by improperly casting a spell, then riding the wave of rogue sorcery released as a result. If the caster can latch onto that excess, some of it can be channeled into specific effects. If the caster loses control, though, the magic will latch onto this world, finding its own form using whatever template is nearest or most convenient to assume, usually the caster himself, in some form or another. The original technique was probably stumbled upon accidentally during a caster's apprenticeship, but once he's learned his art, walking the Broken Path must be a deliberate act. He has to intentionally break the discipline instilled into him. Initiates walking the Broken Path learn to walk on the edge of a blade, trying to gauge just how much power they can safely rechannel. After a while, casters become addicted to the rush of power, the feeling of gambling against the very forces of the universe. It's an adrenaline junkie's dream.
Thoughts on the Broken Path
This is the part I could use some feedback on. I know it sounds a lot like the wild mage of old, but that isn't the flavor I'm looking for. I want this form of magic to be risky and available to anyone foolish or desperate enough to try it. Sure, sometimes beneficial or at least relatively harmless fluff effects will accompany its use. But I want the players to feel like they're playing with fire when they use it, that they're potentially courting their own destruction when they call on this power. It definitely has the flavor of something an arcane caster (especially a spontaneous caster) would use, but I'm not sure I want to limit it to that. There's something appealing to me about a cleric drinking too deep of his god's power in a moment of desperation and things going horribly wrong. There are questions concerning aspects of it as it relates to spontaneous casting vs. prepared casting. I want it to be flexible and tempting for a player to use. If from time to time things seem overpowered, I want to find ways to balance it out by making it extremely dangerous to the caster to use. The Broken Path is all about breaking the rules and then suffering the consequences for it.
The Broken path is meant as a suppliment to the standard d20 magic system and shouldn't have too many bugs left in it.
It's sort of large and ungainly as it stands, so I've put everything behind a spoiler tag to help neaten it up a bit. (yes, I'm learning, I'm slowly learning)
Take a peek and let me know what you think. Most of the hard and fast numbers for DCs and such are by no means set in stone if you think it should be harsher or gentler on the casters, then just let me know.
Basic Mechanics:
Any character with a caster level of 1 and at least one rank in spellcraft or knowledge arcana can fall into the Broken Path. My reasoning: I want it to be accessible to pretty much every caster from the get-go. you won't get the full benefits this way, but it's more to make a chink in the character's armor, setting them up for an even greater fall in the end. A character with only the most basic understanding of the Broken Path can, when casting a spell, declare it to Broken. A Broken spell gains either a bonus of +1 caster level or +2 to the save DC (the player's choice). Ranged touch spells have a -1 penalty to hit, being, at best, clumsily cast endeavors. Now the player has to makes a wisdom check on a d20 versus a DC of {10+(2X spell level)}. (The skill Broken Path Sorcery can be applied here once it is learned.) A failure to meet the DC results in a Flawed spell. Flawed spells are different in some important way to the original. The details are left up to the DM but good examples include randomly changing the spell's energy descriptors, shortening the duration of the spell, strange and lingering side effects like uncomfortable rashes or the temporary growth of fine scales. Feel free to get brutally creative, but don't just drop damage anvils every time. That's what critical failures are for. When a player rolls a natural 1, the Broken spell unravels, blowing up in his face in the form of Backlash. When backlash is incurred, the spell is lost and the character takes some form of damage as rogue mystical energies rebound on him. Some benchmarks could be for the caster to take 1d6 damage per level of the spell cast, or taking a -2 penalty on the character's primary casting attribute per level of spell for 24 hours, Things like that. If you, as a DM come up with something along the vein of a creative curse to have the character labor under, then that works for me, too. It should take the form of some sort of serious smack down. If you decide to incorporate this, I recommend that you refrain from telling your players all the risks involved. Just give them a general idea as to what will happen when they use it. Tell them bad things could happen but don't be too specific. Let them figure the rest out on their own.
New Skill: Broken Path Sorcery (Wis)
Untrained: Yes
Retry: No
Special: Broken Path Sorcery is considered a Cross class skill to every class with spell casting abilities and prohibited to all other classes. It represents the ability to sense and channel unbridled magical energies. A character adds his ranks in this skill to the roll made when casting a spell with the Broken descriptor. Characters gain a +2 synergy bonus if they also have 5 ranks or more of the skill: spellcraft
New Feat: Broken Path Initiate(Broken Path)
Prerequisites: Ability to cast 1st level spells, One rank of Broken Path Sorcery, one rank of either spellcraft or Knowledge: arcana
This character has gained some hard won proficiency with casting Broken Path spells and knows a trick or two about how to avoid getting burned by it.
Benefit:The Skill, Broken Path Sorcery, becomes a class skill, and the character gains an extra 1st level spell as if gained through a high ability score. This spell can only be cast as a Broken spell.
New Feat: Broken Path Adept(Broken Path):
Prerequisites: Caster level 5th+, Broken Path Initiate, 8 ranks of BPS, 5 ranks of either spellcraft or knowledge arcana.
Benefit: The caster has become an adept of the Broken path, and as such, gains a +2 competence bonus to all Broken Path Sorcery Checks. In addition, The bonus given to broken path spells increases to +2 caster level or +4 to save DC, The character gains an additional spell of either 1st or 2nd level as an Initiate does.
New Feat: Broken Path Mastery
Prerequisites: Caster level 10th+, Broken Path Initiate and Adept feats, 12 ranks of BPS, 8 ranks of either spellcraft of Kn: arcana. Must have overcome Spellthirst
Benefit: A master of the Broken Path gains a +4 competence bonus to all Broken Path Sorcery Checks. This replaces the bonus from the Broken Path Adept feat. In addition The bonus to Broken path spells increase to +3 caster level or +6 to save DC. An additional bonus spell can be chosen from levels 1-3 following the same rules as before.
New Feat: Broken Spelltwist (Broken Path/Metamagic)
Prerequisites: Broken Path Initiate, Ability to cast 1st level spells, one rank BPS, one rank spellcraft or Kn: Arcana
Benefit: The character selects three Metamagic feats he already meets the requirements for. He can use the Broken Path to mimic them. Of the three, the player may only select one that has the requirement: "must know 2 other metamagic feats" Unless, of course, the character already possesses two other metamagic feats..then ignore this. Broken metamagic spells don't work in quite the same way as normal metamagic. Broken metamagic is applied the moment a spell is cast, whether that spell be spontaneous or prepared, and takes no real extra time to accomplish. Should it be incorporated when a spell is prepared, the caster must make a broken path sorcery check with a DC of 10(+ the number of hours since it was prepared). The spell is lost when the character fails the roll. Rolling a 1 indicates that 1d4 other spells chosen by the DM are lost as well. Spelltwist takes up a slot of the same level as the original spell, regardless of the spell level the original metamagic feat would call for. However, remember those extra spell levels. For every level the metamagic spell would otherwise occupy, The Broken Path DC increases by 2, as if it actually were taking up a spell slot of the higher level. Broken Path metamagic feats and normal metamagic feats cannot be applied to the same spell. The conflicting energies causes the spell to be lost and deals 1d4 damage to the caster per spell level. (this included the phantom levels applied by Spelltwist)
Spelltwist can be taken multiple times, each time selecting three new metamagic feats to mimic
New Feat: Blood from a Stone (broken path)
Prerequisites: Caster level 1st, One Rank Spellcraft or KN: arcana, one rank BPS, Con 13+, Ability to cast spell spontaneously
This character can, at a cost to his health, cast more spells than he'd usually be able to manage.
Benefit: The caster may take two points of constitution damage per spell level to cast a spell without using up a spell slot. This spell can be of any level known to the character as long as the resulting Con damage wouldn't drop the character's modifier below 0. 0 level spells count as 1/2 of a level for determining constitution damage. The character may cast in this fashion as long as he still retains a positive Con modifier. Once his modifier reaches 0 then he has exhausted this route. As a secondary drawback, Blood from a Stone causes a form of backlash that fills the caster's body with uncontrolled sorceries.This means the character cannot be healed magically until he naturally recovers all of his lost Con points.
New Feat: Shattered Chains (metamagic?/Broken path)
Prerequisites: Broken Path Adept, Broken Path initiate, Caster level 5th+, etc...
I don't know if this one should be considered metamagic or not.
The character can cannibalize existing spells, breaking them down into raw energy that can be directed as a crude, but potentially powerful weapon.
Benefit: Upon the successful attempt of a Broken Path Sorcery check, {DC = 10 plus (2x spell level) +2 },The caster tears the bonds containing his own uncast spells. The resulting blast can be directed in a quarter circle, dealing damage indiscriminately to all legitimate targets within a range of 10 feet (+5 feet per caster level) The damage done is equal to 1d6 X the sacrifices spell's level. The caster takes 1 point of damage per spell level as well. The damage has no energy descriptor. It's just raw, barely controlled power. A failed check resulting in a flawed spell sends the blast into a random direction. or adds some other random effect to the blast. (survivors gaining temporary damage resistance, something like that) A natural 1 detonates the power within the caster's body, causing them to take the full brunt of the damage. This replaces the normal effects of basic broken path sorcery (ie the bonus to caster level or Save DC)
The Pitfalls of the Broken Path:
Flawed spells: When a character fails a Broken Path Sorcery roll he creates a flawed spell. These spells still work, but never accomplishing the expected results. A Flawed spell is completely in the hands of the DM. Here are some suggested flaws. Energy descriptors can be exchanged in any spell that has them. Fireballs could instead to cold or sonic damage. Targets of damage spells could find themselves with a temporary immunity or resistance to some quality associated with or opposed to that magic. Someone hit with a fireball could be granted cold resistance or fire resistance. The DM can feel free to change the target of the spell or to have area spells hit in the wrong place/ direction. Healing spells, while fixing damage, might leave horrific scars or discolored birthmarks behind. Necromantic spells might accidentally raise fallen targets as uncontrollable undead. Summoned creatures might not obey the caster, attack him on sight, etc. A kinder gentler DM might just settle for strange lights accompanying the casting along with peculiar odors or screeching sounds. But that, in my honest and never humble opinion, just isn't all that much fun.
Backlash: When a character rolls a 1 on a BPS check, the spell is lost and the caster suffers backlash. simple backlash can take the form of 1d4 or 1d6 damage to hp per level of the spell attempted. You want it to hurt, potentially a lot, but maybe not kill them outright. Be willing to fudge a little especially early in the game when a first level wizard botches the roll and then gets hit with a 4....dead wizard. Other options could include 2 points of damage to a character's primary spellcasting attribute per spell level. Having some of the Flawed spell effects hit the caster during backlash can lead to interesting twists. You might also drop a curse of some sort on the character for a brief time. Backlash effects shouldn't last more than 24 hours, but if you find a good one that you think should be semipermanent, then go right ahead with it.
Spellthirst: Keep track of every time a caster receives backlash. Mark a little point on your notes or something. These magical energies begin to accumulate in the body. The only way to decrease backlash is to refrain from casting broken path magic. Backlash fades at a rate of one point per month until it's back at 0. Using the broken path at any time starts the clock back to the beginning of the month. As these magical energies slosh around, the caster becomes more and more dependant on them. It becomes an addiction. If at any time, the number of Backlash points exceeds the caster's highest ability modifier, then he acquires the curse of spellthirst. A character under the influence of spellthirst acts as if constantly fatigued unless he voluntarily sacrifices a spell every twenty four hours. A 0 level spell will assuage the spellthirst, but higher level spells give the character a temporary bonus to strength equal to the level of the spell sacrificed. This bonus fades quickly, lasting only 10 minutes (+1min per caster level) A spellthirsting character can sacrifice as many spells as he wishes per day.
The only known way to break a caster of spellthirst is for them to go cold turkey and not use magic of any sort for a month. This includes wearing or carrying magical items. The caster's body needs time to let all that accreted power work its way out. At this point, backlash goes down to one point below spellthirst levels and will decrease as normal following the rules above. Being targeted by magic doesn't have an effect on breaking spellthirst.
Playtesters are welcome, though if you use it, drop me a pm or something and give me a little feedback