Homebrew Item, Meant to let Level 5 Party Take on an Adult Greed Dragon (CR 15)

[Alexander Atoz]

I wrote an adventure for my blog, and the climax is meant to be the players facing down an adult green dragon after getting a magic weapon specifically built for this battle.
Do you think this is enough to do it?

Longbow of [Green] Dragon’s Bane:
The bow is a legendary item. When used against a dragon*, it has the following properties: + 5 to hit, + 15 damage, grants proficiency to its user if they didn’t have it [for use with itself only]. When hit with a bolt from this bow, the dragon is weakened, suffering disadvantage on all its attack rolls and saving throws, it loses 2 AC, and it becomes vulnerable to all damage types that it isn’t immune to. Also, it goes down to a single legendary action a round. Since this would make wing attack impossible, wing attack now only costs 1 legendary action.
This assumes 4 level 5 players. If your players are levels 3-4, you should raise the stats to:
+ 35 damage, halves the damage that the dragon deals while affected. (Since the dragon rolls two dice with all its attacks, just lower it to 1 dice plus half STR.) Everything else is the same as before.
In addition to the above, they’ll need potions and/or scrolls with the power to heal each of them back to full health, and a potion of resistance to poison damage. I’d give each of them one of each potion. (Unfortunately, then they’ll defeat the dragon without them, and use them on a different quest, but some stuff you just have to live with.)

* You can decide if it affects other dragons, or just green ones. The second is probably smarter.

For whatever reason, the dragon will be without lair options. I still have to figure out way.

(Disclaimer: as mentioned above, this is to use on a blog.)

[DeTess]

I think the breath weapon still risks a party kill, as do bad rolls on frightful presence. There's also the issue of the player with the bow feeling awesome, and everyone else just kinda being there.

I've run something similar a while back, but I gave every player an boon for the fight (Modron warlock got to borrow a Modron battle suit, ranger got to borrow an anti-dragon rifle, the guy possessed by a fey wolf god (long story) let the wolf out to play, druid associated with aforementioned wolf god brought in a stream of reinforcements, etc.)

I also homebrewed the monster to have these big telegraphed attacks instead of traditional aoe's that the players could dodge, so the risk of a bad breath one shotting everyone was reduced.

For your case, I'd give every player some dragon killing boon, and maybe adjust the dragon a little to reduce the risk of the breath ending the fight in a single go.

[Just to Browse]

To add to what DeTess said about breath weapons, the average damage here is 56. A decently-optimized wizard has about 30 HP. Even if the arrow halves the dragon's breath weapon damage in addition to all the other stuff it does, you're talking about a failed save potentially one-shotting fragile members of the party. As soon as that breath weapon recharges,multiple people are probably going down.

To your specific question - I think this you may be designing in the wrong direction. I wouldn't think of this like designing a homebrew item. After all, would your adventure expect the PCs to fight this dragon without this bow? If the answer is no, the bow isn't like a normal magic weapon from the DM's perspective, it's a plot tool.

You'll be better off designing the monster first, then writing your magic bow's effects to fit. Think about the statblock of the dragon that you want the PCs to fight. What CR should it be? What is its HP? What is a CR-appropriate breath weapon attack? What are its legendary actions? You can use the existing green dragon statblocks for inspiration, or just build it from scratch.

Once you're satisfied with your statblock, go back and note how this is different from the green dragon statblock, and state that your bow of green dragon's bane applies those differences to any green dragon it hits. In the appendix of your adventure, you can include the new statblock as a "weakened adult green dragon", which will be especially nice for DMs trying to run the thing quickly.

A few other tips to consider here:

• The Reduced-Threat template from Tales from the Yawning Portal roughly cuts 2 points of CR off a given monster. That might be useful to look at.
• I would avoid giving persistent disadvantage to your boss monster, because disadvantage & advantage don't stack. Any PC abilities that apply disadvantage (e.g. frostbite, the dodge action) become less useful in this fight, which can be unintuitive.
• Since this is for an adventure, you can't guarantee party composition. It's possible that your adventure will be played by a party where no one has longbow proficiency. You may want alternative ways to weaken the dragon so that this fight goes more smoothly.
• If you can, I suggest using a young green dragon here. Its CR is much more reasonable (CR 8), and while its breath weapon still deals a monstrous 42 points of damage, it probably won't instakill the party wizard if you halve the damage.

[rel]

I second creating a CR appropriate statblock and then have a plot device 'depower' the dragon to that.

It needn't even be a bow; finding and breaking a phylactery or equivalent (like a soul in a hens egg), tricking the dragon into breaking an oath, or fulfilling the conditions of an ancient prophecy are all thematically appropriate de-powering activities.

[Alexander Atoz]

A few of these are stuff I dealt with. I specified that the players will need potions of poison resistance, (meant for the breath weapon, although I didn't say it straight out).
I specified potions/scrolls of full healing, 1 per player, so that they could raise the fallen players and to reduce the risk of player death. I also stated that the longbow grants proficiency to its user.
I didn't think about the possibility of one player being OP at the price of the rest. I didn't think about the fear, or disadvantages not stacking. I'd like to ask about each of them.

1) Do others also feel that this will cause an unfair spotlight to one player? (That player isn't doing that much damage, maybe twice of anybody else, but they will still need the others if they're to have any chance of winning. Also, they aren't getting to use their class powers, unless they're built around archery.)
2)Why do you feel that fear will cause such problems? It uses up the dragon's turn to cast it, and I'll remind you that I've greatly reduced its legendary actions.
3)How many player skills/spells/items/whatever cause disadvantage? (You were worried that it would make such abilities useless.)

[Alexander Atoz]

A few of these are stuff I dealt with. I specified that the players will need potions of poison resistance, (meant for the breath weapon, although I didn't say it straight out).
I specified potions/scrolls of full healing, 1 per player, so that they could raise the fallen players and to reduce the risk of player death. I also stated that the longbow grants proficiency to its user.
I didn't think about the possibility of one player being OP at the price of the rest. I didn't think about the fear, or disadvantages not stacking. I'd like to ask about each of them.

1) Do others also feel that this will cause an unfair spotlight to one player? (That player isn't doing that much damage, maybe twice of anybody else, but they will still need the others if they're to have any chance of winning. Also, they aren't getting to use their class powers, unless they're built around archery.)
2)Why do you feel that fear will cause such problems? It uses up the dragon's turn to cast it, and I'll remind you that I've greatly reduced its legendary actions.
3)How many player skills/spells/items/whatever cause disadvantage? (You were worried that it would make such abilities useless.)

My thanks to the feedback of everyone who commented.

[DeTess]

1) to put it simply, yes. Ina full party odds are good someone can use a bow well, and they'll be the standout character in this encounter.
2) because it is a very potent control tool, and could be used while the dragon is still some distance away. As a DM I'd open with either frightful presence or a breath, then follow with the other one on the next turn.
3) I don't really follow this question.

If I were you I'd either go the 'depower through plot device' route, or the 'empower through plot device' route. Both ensure no player is naturally advantaged, either by bringing the dragon down to their level, or the players up to the dragons level. This way also should avoid the dragon's remaining abilities causing too much trouble.

[Just to Browse]

That prep sounds decent. To be clear, I don't want my comments to come across as "you have done this wrong, you buffoon, you absolute fool". It's just that a lot of folks try what you're planning at least once in their DMing career (setting a fight against a very strong monster, hacking in a mixture of nerfs, targeted loot, & exploitable weaknesses to make the fight easier) and there are a few ways it can go poorly. I run this style of adventure a lot because I like putting higher-level monsters in lower-game games, and I've seen this crop up a fair bit:

• One player is a standout because they get the mcguffin so everyone else feels useless.
• The players don't actually find the targeted loot, or they forget to use it, or they misjudge its value, and get stomped.
• The monster isn't nerfed enough, or not nerfed in the right ways, and the players get stomped.
• The monster is over-nerfed so the monster gets stomped.
• The monster is such a massive portion of the XP budget that it doesn't get minions, so it gets stomped.

There's a chance you won't run into these issues, but there's always a chance that you will. Ideally, you minimize the risk of stuff going wrong by designing the challenge backwards, adding robust clues, and finding ways for party members to share the spotlight.

Specifically RE: question #3, here are the spells that could apply disadvantage to the dragon's attacks, ability checks, or saving throws, which are available to lv5 PC, are frostbite, vicious mockery, hex (ability checks), blur, compelled duel, web, maximilian's earthen grasp, entangle, ensnaring strike, fog cloud, blindness/deafness, invisibility, cause fear, and wrathful smite. Outside of that, you've got the Dodge action (most likely just for monks), Ancestral Barb's Ancestral Protectors, Light Cleric's Warding Flare, Battlemaster's Goading Attack & Menacing Attack, and the Oathbreaker's Dreadful Aspect.

[DeTess]

So, to add slightly more constructive feedback:

If you want to give some kind of reward weapon for making the fight easier, how about a set of these (one for each player):

Dragonslayer's armament
Weapon (any), rare (requires attunement)
You have a +1 bonus to attack and damage rolls made with this magic weapon.

Once per short rest, the wielder can cast absorb elements as a 1st level spell as a reaction.

Dragonslaying ritual: Someone attuned to the weapon can perform a ritual to call on the wisdom and experience of those that wielded the weapon before them. The ritual takes 10 minutes to perform, and requires precious gems worth 1000 gp (either rubies, emeralds, onyxes, diamonds or sapphires), which the ritual consumes. After the ritual the wielder gains 50 temporary hitpoints and the following benefits until their next long or short rest, which only apply against dragons whose scales match the color of the sacrificed gems:

• When the wielder is attacking a dragon they add 1d4 to their attack rolls.
• when the wielder makes a safe against an ability from a dragon, they add 1d4 to their roll.
• when a dragon makes an attack against them, they subtract 1d4 from their roll.
• when a dragon makes a safe against a spell or ability from the character, they subtract 1d4 from their roll.
• Dragons are vulnerable against damage dealt by the wielder.

Some numbers might need tweaking, but the idea is to give the characters the benefit of bless and the dragons the malus of bane, as well as extra damage. The ritual is expensive and specific enough that the players won't perform it often outside of this use case, where you can provide the gems in advance.

[Alexander Atoz]

Thanks to everyone. This has been awsome.

I would like to ask. You said

The monster is such a massive portion of the XP budget that it doesn't get minions, so it gets stomped.

I understood the rest, but I'm not sure I understood this one. Is it meant only for cases where the monster is a spellcaster [or the like] that needs minions, such as a lich or mummy lord? If it's meant for all monsters, then I don't understand.

To DeTess:
Thank you. I really like your dragonslayer's armaments, and I'd consider using them. As this is for a blog, not just for personal use, I feel that I need to ask permission. Would you be okay with my using your idea? (I assume its yours. I checked on D&D Beyond too verify that it isn't offical content, but if it belongs to someone else please let me know, as I'd need permission.)

[DeTess]

To DeTess:
Thank you. I really like your dragonslayer's armaments, and I'd consider using them. As this is for a blog, not just for personal use, I feel that I need to ask permission. Would you be okay with my using your idea? (I assume its yours. I checked on D&D Beyond too verify that it isn't offical content, but if it belongs to someone else please let me know, as I'd need permission.)

As far as I know it's my own original content. Feel free to use it for your blog, as long as you give some form of credit.

[Just to Browse]

I understood the rest, but I'm not sure I understood this one. Is it meant only for cases where the monster is a spellcaster [or the like] that needs minions, such as a lich or mummy lord? If it's meant for all monsters, then I don't understand.

A common pattern in these boss-fight-style combats is that a single powerful enemy faces off a group of 3-5 people opposing it. Frequently a fight that is "balanced" results in enemies that have lots of damage, but don't have enough HP and are susceptible to controlling effects (abilities or spells that e.g. stun, blind, frighten). In general, you should include minions in boss fights to mitigate these problems.