Off-Beat Magic Items.

[Cyrano101]

Inspired by pages like this: manysideddice.com/2015/03/10/a-table-of-contents-thats-better-than-nothing/ I set out to create some magic items that would be reasonably powerful, but also have the kind of drawbacks that would make their use an interesting choice. My goal was to create items my players would enjoy using, but would have to think carefully about in order to get the most out of them. I'm curious what the forum thinks of what I have so far, and if there are any obvious pitfalls or exploits that I am missing. If you like what you see feel free to steal, they're just things I have been tinkering around with.

Spoiler: Nyrkul's Wager

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Nyrkul's Wager
Weapon (spear), very rare major item (requires attunement)
You gain a +2 bonus to attack and damage rolls made with this weapon.
Nyrkul's Wager is a bronze spear. Much of the haft is heavily tarnished, and it is dotted with barnacles and mussels along its entire length, as if it had been left underwater for a long time. Despite this, the spear has a natural heft to it, and both the weapon itself and the creatures that cling to it appear to be immune to harm.
Beloved of the Sea. While wielding this spear you have a swimming speed of 30 ft., and can hold your breath for up to eight hours at a time.
Try your Luck. At any time while you are attuned to Nyrkul's Wager, you can use a bonus action to cause a thick foam to bubble out of the barnacles and mussels that line its haft. This foam deals 6d6 Acid damage to you. Then, if you hit with your next attack, in addition to the damage that attack would normally do, Nyrkul's Wager deals an amount of Force damage to the target equal to the amount of Acid damage you took when you activated this ability.
Additionally, if your next attack after activating this ability is a Critical Hit, you gain a number of Temporary Hit Points equal to the total damage dealt by that attack.

Spoiler: Cinder Cape

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Cinder Cape
Wondrous item), uncommon major item (requires attunement)
This bright, scarlet cape constantly shimmers, as if from extreme heat.
Warding Flair. As a Reaction, when you take any amount of Fire damage while you are wearing the Cinder Cape, you can impose the cape between yourself and the source of it to prevent half of that damage. When you do so, mark down the amount of damage the cape prevents, and it gains one Charge. You cannot use this ability again as long as it has that Charge.
Searing Flourish. As a Bonus Action, you may expend one Charge from the Cinder Cape and flourish it to send a wave of heat and flame flowing out from you in all directions. When you do so, each creature in a 30 ft. radius around you must a DC15 Dexterity Saving Throw, taking fire damage equal to the amount the cape prevented when it gained that charge on a failed save, or half as much damage on a successful one.

Spoiler: Cloak of the Butterflies

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Cloak of the Butterflies
Wondrous item, uncommon major item (requires attunement)
This iridescent cloak is composed of the wings of thousands of butterflies. Originating in the Feywild, it is said that these cloaks are made by pixies as a way to honor their fallen comrades.
Totally Fabulous. As an Action, you may attempt to Charm one creature of your choice that isn't hostile to you. That creature must make a Wisdom Saving Throw, with the DC equal to 8 + your Proficiency Bonus + your Charisma Modifier. On a failed save, the creature become Charmed by you for 1 minute. At the end of that time, or if it makes its Saving Throw, it becomes aware that you used this ability, but it cannot hold it against you. You may activate this ability once per Short Rest.
Born on a Thousand Wings. As an Action, you may give yourself a flying speed of 25 feet. This effect lasts for 1 minute and can't be used again until the next dawn.
Fragile Beauty. If you take damage while wearing the Cloak of the Butterflies, its magical abilities cease to function until the Mending cantrip has been cast upon it 3d8 days in a row.

Spoiler: Dance Pants

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Dance Pants
Wondrous item, legendary minor item (requires attunement)
These gleaming, diaphanous, golden silk pants catch the eyes of anyone who sees them.
Can't Touch This. As an Action, you can begin to dance, Concentrating on your performance as you would a spell. Each turn you can use your Action to continue this dance or choose to stop dancing. So long as your dance continues, in order to attack you a creature must first make a contested Performance Check against you. If it loses that Check it cannot attempt to make an attack against you until the beginning of its next turn. You may activate this ability once per Short Rest.

Spoiler: Life Snaggers

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Life Snaggers
Wondrous item, legendary minor item (requires attunement)
As long as you wear this snug pair of gloves, your hands always stay comfortably warm. When a creature within 30 ft. of you fails its last Death Save, you can immediately use your reaction to snap your fingers and give that creature one additional Death Save. Each time you do so the Life Snaggers gain one additional Charge. At the beginning of your next turn you must make a Wisdom Saving Throw, with the DC for this throw equal to 10 + the number of Charges the Life Snaggers have. On a failure, the they transform into a cloud of dandelion seeds.

Spoiler: Slickscale Suit

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Slickscale Suit
Wondrous item, legendary minor item (requires attunement)
While you wear this lime-green, scaled suit, you have advantage on all Ability Checks and Saving Throws made to escape being Grappled and Restrained. Additionally, once per Long Rest you can make your full Movement through a space large enough for a small snake.

Spoiler: Fate Eater

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Fate Eater
Weapon (battleaxe), artifact (requires attunement)
The long, twisting handle to this grim weapon is made from blackened wood, carved with countless depictions of torment. Some of these carvings are little more than wailing faces, while others reveal detailed diagrams of torture. The axe's blade is made from a thin, curving sickle of bone, which radiates a frigid chill.
Random Properties. The axe has the following randomly determined properties:
2 minor beneficial property
1 major beneficial property
1 minor detrimental property
2 major detrimental properties
Author of Bloodshed. For each Charge Fate Eater has, you gain +1 to your Attack and Damage Rolls. It can have a maximum of 3 Charges.
Consume Fortune. While attuned to Fate Easter, as a reaction, you can give any creature you can see Disadvantage on any Attack Roll, Ability Check, or Saving Throw. They perceive this effect as a sudden, spreading numbness from their heart. Whenever you activate this ability, Fate Eater gains 1 Charge, and then you take Necrotic damage equal to 5 times the number of Charges it has.
Frightful Aspect. As a Bonus Action, you may expend 1 of Fate Eaters Charges to gain Advantage on Intimidation Checks, Stealth Checks, and Constitution Saving Throws for one hour. Each time you expend a Charge from Fate Eater in this way, you take 5 Necrotic damage. While this effect is active, when you speak your voice echoes with the voices of thousands, your skin pigmentation becomes more vivid, your eyes turn pitch black, and your shadow no longer perfectly mirrors your movements.
Dread Eternity. Any creature slain by Fate Eater when it has 3 Charges appears 4d12 hours later as a new carving on its handle. Once a creature has appeared there, it cannot be restored to life by any means save the Wish spell or similar magic.
Gatecarver. While you are attuned to Fate Eater, you have the power to conduct a Ritual that opens a portal from the Material Plane to the Shadowfel, or from the Shadowfel to the Material Plane. To do this, Fate Eater must have three Charges, and you must have access to a freshly-slain humanoid corpse. The Ritual takes ten minutes, and at the end of that time all of Fate Eater's Charges are expended, and the corpse transforms into the portal. This portal remains in place for one hour, and then closes. Any area where you have completed this Ritual becomes Desecrated Ground.
Destroying Fate Eater. It is actually relatively easy to destroy Fate Eater, any blow of sufficient strength with a magical weapon will snap its haft, at which point the rest of it crumbles into ash. However, whenever Fate Eater is destroyed it reappears 1d10 days later in the home of someone who is contemplating killing a loved one. The legends say that the only way to rob Fate Eater of this ability is to strap it into a plow and use it to till the fields until it has provided as many harvests as it has taken lives.

Spoiler: Starlight Spectacles

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Starlight Spectacles
Wondrous item, very rare major item (requires attunement)
The lenses on this pair of round spectacles glitter with stars set into a beautiful, purple night sky.
Stargazer. While wearing these spectacles you have advantage on Initiative Rolls, and on all checks made to navigate or avoid becoming lost.
Illumination. Whenever you make a ranged melee attack that requires ammunition against a hostile creature while attuned to this item, you can use a bonus action to cause your ammunition to glow as if under the effects of the Light spell. If the attack hits, your target has disadvantage on all Stealth Checks until it uses an Action to remove that piece of ammunition from its body. Each time you use this ability the Starlight Spectacles gain 3 charges.
Falling Stars. At any time while you are attuned to the Starlight Spectacles you can use an action to cast Magic Missile as a 6th-level spell. Using this ability causes the Spectacles to gain 10 charges. Once you use this ability, the Spectacles lose all magical properties until the end of your next Long Rest.
Total Awareness. So long as the Starlight Spectacles have 67 Charges or more, you gain the benefits of the Haste spell.
Glimpse the Beyond. If the Starlight Spectacles have any Charges when you complete a Long Rest, roll Percentile Dice. If the number rolled is less than or equal to the number of Charges they have, the Spectacles immediately lose all of them, and you gain one random form of Long-Term Madness (DMG: 260). Additionally, roll one d20 and record the number rolled. Until your next Long Rest, you can replace any Attack Roll, Saving Throw, or Ability Check made by you or a creature you can see with that roll. If the number rolled on the Percentile Dice is greater than the number of Charges the Starlight Spectacles have, they instead gain 5 more Charges.

Spoiler: Huntcaller

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Huntcaller
Wondrous item, uncommon major item (requires attunement)
This leather circlet is adorned with a pair of swept-back deer antlers, their points capped with gold. Where the ends of the antlers meet sits a large emerald set in golden amber.
Voice of Command. While you are wearing Huntcaller you can use an Action to cause your voice to boom and echo as if under the effects of the Thaumaturgy spell. While this effect is active you make all Persuasion Checks with Advantage. You can dismiss this effect at any time as an Action. Immediately after the effect ends you completely lose your voice for 2d12 hours. Your voice can be restored with a Greater Restoration spell or similar magic.

Spoiler: Storm and Anchor

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Storm and Anchor
Weapon (shortswords), rare major item (requires attunement)
Storm and Anchor are a pair of matched shortswords. When you study Storm in direct light, you can see faint images of storm clouds roiling beneath its surface. Likewise, a close study of Anchor reveals infinitely spiraling chains. When you strike a single opponent with both blades, they create a unique magical effect depending on in what order they strike their target.
Storm's Fury. When you strike first with Anchor, after you roll damage a chain and anchor leap out of the blade to wrap around your target's chest. If you hit that target with Storm before the end of your turn, a storm cloud immerges from within the blade, and lighting arcs from it into the chains wrapped around your target, dealing an additional 2d8 Lightning damage.
Sea's Revenge. When you strike first with Storm, after you roll damage a dark storm cloud immerges from within the blade. Rain from this cloud slicks the ground beneath your target's feet as it drifts upward to linger around their head. If you hit that target with Anchor before the end of your turn, after you roll damage a chain and anchor leap out of the blade to wrap around your target's chest. If your target is Large or smaller, they slip on the water beneath their feet, and the anchor knocks them Prone.
Regardless of whether their other effects take place or not, the anchor, chain, and storm cloud all fade away at the end of your turn.

Spoiler: Swift Stormwrought

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Swift Stormwrought
Weapon (shortsword), legendary minor item
Swift Stormwrought is a gently curved wooden shortsword, made from darkened driftwood long ago worn smooth by the passage of the tides. When Swift Stormwrought is used to make an Attack of Opportunity, if that attack hits, you regain the use of your Reaction.

Spoiler: The Lovers

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The Lovers
Wondrous item, rare major item (requires attunement)
A matched set of silver coins. On one side they are both decorated with a pair of trees, their roots and branches deeply intertwined. On the other side they each depict the profile of a different face. If you are married or have a passionate lover, one of them depicts your own profile and the other your partner's. If you have no such connection, they depict a pair of elfish youths instead.
Reunion. If the two coins are separated, so long as they are within 10 miles of one another, you can use a Bonus Action to flip whichever one of them is in your possession. As you do so, you may choose 2d6 willing creatures within 60 ft. of you. Immediately after you catch the coin, you and each creature you designated teleport to the location of the other coin in a flash of dusky pink light and a shower of rose petals.

Spoiler: Respect Authority

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Respect Authority
Weapon (whip), rare major item (requires attunement)
You gain a +2 bonus to attack and damage rolls made with this weapon.
Respect Authority is a whip made from a translucent, red spinal column. It smells faintly of brimstone, and always feels faintly warm to the touch. The weapon's grip, bound with a strange, pale leather, has its name burned onto it.
Extraplanar Origin. You are immune to the environmental effects of Extreme Heat.
Irresistible Command. When you hit a creature with a Melee Attack using Respect Authority, you can compel that creature to use its Reaction to make one Melee Attack against a creature of your choice within range. If that creature has no melee weapons, it must make an unarmed strike. If there are no creatures within your target's melee range, you cannot use this ability.

Spoiler: Inequalizers

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Inequalizers
Wondrous item, uncommon major item (requires attunement)
This pair of black, fingerless gloves have segmented, iron bands that wrap over their knuckles. while wearing them, you gain +1 damage to all damage rolls. Additionally, once per short rest, you may slam your knuckles together to gain the enlarge effects of the enlarge/reduce spell. While you are enlarged, you add +2 to your damage rolls instead of +1.

Spoiler: Swamp Boots

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Swamp Boots
Wondrous item, legendary minor item
These perpetually filthy boots are somehow always caked with wet mud, leaving a trail behind you that fades away after a few seconds. While wearing them your movement speed is reduced by 5 feet, but you ignore the effects of difficult terrain, quicksand, and similar environments. Additionally, you have Advantage on Checks and Saves made to avoid being moved against your will.

Spoiler: Arcane Wellspring

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Arcane Wellspring
Wondrous item, rare major item (requires attunement)
The buckle to this ornate, leather belt depicts a well with three bright, glowing gems leaping out of it.
This belt has 3 Charges. When you expend a Charge from the Arcane Wellspring you can restore the following: one use of a Rage, Channel Divinity, Wildshape, or Arcane Shot, one Bardic Inspiration or Superiority Dice, one Ki or Sorcery Point, one once-per-long-rest Eldritch Invocation or Racial Ability, or one 1st-level Spell Slot. You may also pass a charge from the Arcane Wellspring on to an ally, who can use that Charge in any of the same ways. The belt regains all expended Charges daily at dawn.

Spoiler: The Scribe

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The Scribe
Wondrous item, rare major item (requires attunement)
This band of worn leather is designed to be used as a weapon's grip. Any weapon that is bound by the Scribe is considered a magic weapon.
Uncanny Scroll. The Scribe can be used as a Spell Scroll. When it is used in this way the inscription process takes half the amount of time that it would usually take. Unlike a normal Spell Scroll however, it is impossible to cast the spell inscribed upon it in a normal manner. Additionally, that spell can be erased from the Scribe over the course of an hour by scrubbing it thoroughly in fresh, untainted water.
Battle Magic. When a weapon bound with the Scribe hits a creature with a melee or ranged melee attack, you can immediately use your reaction to cast whatever Spell is currently inscribed upon it as if you were casting it from a Spell Scroll. If that spell is 3rd-level or lower this ability cannot be used again until you take a Short Rest. If that spell is 4th-level or higher this ability cannot be used again until you finish a Long Rest.

Spoiler: Ironheart

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Ironheart
Armor (breastplate), very rare major item (requires attunement)
While wearing his armor, you gain a +1 bonus to AC, and Resistance to Cold damage.
Ironheart is an iron breastplate, with an unholy, snarling face on its chest. In this twisted visage's right eye rests a small, faintly glowing, blue gem. Its left eye on the other hand is a fist-sized chamber covered with a seemingly indestructible pane of glass. Within this small chamber you can see a steadily beating mechanical heart.
Arrhythmic Beat. In order to attune to Ironheart you must spend one Long Rest wearing it. At the end of that Long Rest, Ironheart attempts to forcefully bring the rhythm of your heart in alignment with its own. You must make a DC15 Constitution Saving Throw. On a success you attune to Ironheart. On a failure however you take 3d12 Cold damage, and you do not attune to Ironheart.
Icy Resolve. Whenever you drop to 0 Hit Points while you are attuned to Ironheart, you do not fall Unconscious. You must continue to make Death Saves as you normally would, stabilizing if you succeed three times, but you do not fall unconscious as a result of having 0 Hit Points. While in this state the relentless rhythm of Ironheart's beating heart actually increases your abilities, giving you advantage on all Attacks and Ability Checks. However, the stress this places on your body makes resisting hostile effects more difficult, and you have disadvantage on all Saving Throws, including Death Saves. These effects end whenever you have more than 0 Hit Points.

Spoiler: Retribution

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Retribution
Weapon (shortbow), rare major item (requires attunement)
Retribution is an unstrung golden bow with a grip of bronze dragonscale. You gain a +1 bonus to attack and damage rolls made with Retribution.
Bolt. When you nock an arrow to Retribution, a strand of lighting forms its bowstring. Any arrow you loose with Retribution deals Lightning damage instead of its normal type.
Vengeance. While you are attuned to Retribution, when a creature deals damage to you, you can use your Reaction to mark them for vengeance. You can only mark one creature at a time, but you can dismiss any previous mark you have when you use your Reaction to mark a new enemy. Otherwise your mark fades after one hour. You instantly recognize a creature you have marked for vengeance, even if they are in disguise. When you attack a creature you have marked for vengeance, they gain no benefit from cover, other than total cover, and you suffer no disadvantage when attacking them due to long range. Additionally, when you roll for damage against a creature you have marked, you roll 2d10 Lightning damage instead of the usual amount.
Smite. When you have marked a creature for vengeance with Retribution, you may use it to cast the Lightning Bolt spell targeting the creature you have marked. After you use this ability you must make a DC12 Constitution Saving Throw or become Blinded. You can repeat the Saving Throw at the end of each of your turns, ending the Condition on a success. Once you have used this ability, you may not use it again until the next dawn.

Spoiler: Agony's Delight

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Agony's Delight
Wondrous item, uncommon major item (requires attunement)
This apple-sized fruit is vividly red, and has a sheen to it that looks almost metallic. Eating the fruit restores half of your maximum Hit Points, and, so long as you have less than half of your maximum Hit Points when you try to eat it, it has a pleasantly sweet flavor. Each time you eat Agony's Delight, an identical fruit appears beside you when you awake the next morning. You are also attuned to this new fruit.
However, if you have more than half of your maximum Hit Points when you try to eat Agony's Delight, its sweet flavor becomes cloying and overpowering. In order to finish eating it you must succeed on a DC18 Constitution Saving Throw. On a success you are able to force yourself to finish the fruit. On a failure however, you choke on the last bite and are forced to cough it back up. Upon leaving your mouth, that bite instantly dissolves into green ichor.
When you choke on Agony's Delight you still regain enough Hit Points to restore you to full health. However, sometime over the course of your next long rest you awake at 0 Hit Points, choking on your own vomit, with one Failed Death Save. You must make the remaining Death Saves as normal. You do not gain the benefits of a Long Rest from that night's sleep and can only benefit from a single Short Rest during that time. Additionally, when you awake the next morning, there are two copies of Agony's Delight beside you instead of one. You are attuned to both copies of the fruit, randomly displacing one of your other attunements if you are already attuned to three items. If you are already attuned to three copies of Agony's Delight, you still awaken to a new copy of the item resting alongside you, but you are not attuned to it. If you ever go an entire day without eating Agony's Delight, this same effect occurs.
Agony's Delight cannot be destroyed by any means except eating it, and to creatures not attuned to Agony's Delight it always tastes vile. A creature not attuned to Agony's Delight must always make a DC18 Constitution Saving Throw to eat it. If they succeed, they lose an amount of Hit Points equal to half their Hit Point Maximum and the Fruit is destroyed. If they fail however, they lose an amount of Hit Points equal to half their Hit Point Maximum, and the next morning they awake to find a copy of Agony's Delight that they are attuned to resting alongside them, randomly displacing one of their other attunements if they are already attuned to three items. If they are already attuned to three copies of Agony's Delight they still awaken to a new copy of the item resting alongside them, but they are not attuned to it.
Curse. Once you are attuned to Agony's Delight, you can't end your attunement to it unless you are targeted by the remove curse spell or similar magic.

Spoiler: Righteous Soulfire

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Righteous Soulfire
Wondrous item, very rare major item (requires attunement by a spellcaster)
This purple armband bears a silver flame emblem on a small medallion decorated with eight amethyst gems.
Soul Power. Each of the gems on Righteous Soulfire's medallion can be charged by spending one hour Concentrating on it, as if Concentrating on a spell. At the end of that hour, make a DC12 Constitution Saving Throw. On a success, 2 of your Hit Dice are expended and Righteous Soulfire gains 1 Charge. On a Failure 2 of your Hit Dice are still expended, but Righteous Soulfire gains no Charge.
Righteous Magic. Whenever you cast a spell while you are attuned to Righteous Soulfire, you may expend as many of its Charges as you want to increase the level of your spell. The spell's level increases by the number of Charges you expend. When you activate this effect, you must call out Righteous Soulfire's name, and its medallion blazes with silver flame. When you increase a spell's level with Righteous Soulfire, it cannot be Subtle.

Spoiler: Felicity's Candle

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Felicity's Candle
Wondrous item, legendary minor item
When you light this candle, a willing creature that you designate is endowed with a peculiar form of luck. Once lit Felicity's Candle burns for one hour, and it cannot be extinguished by any means. For as long as the candle burns, the designated creature has advantage on all Attack rolls, Ability Checks, and Saving Throws.

Spoiler: Sweet Freedom

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Sweet Freedom
Wondrous item, legendary minor item (requires attunement)
This small, grey ring is seemingly made of stone, but when you put it on it resizes to fit your finger exactly.
If at any point while you are wearing Sweet Freedom you fail a Saving Throw, you may choose to succeed instead. If you do so, Sweet Freedom tightens, dealing 5 slashing damage to you and severing the finger it is on. This damage cannot be prevented, and the finger cannot be reattached by any means other than a Wish spell. After it is used Sweet Freedom drops from your hand. It can be caught with a DC14 Sleight of Hand Check. Once you have lost the majority of the fingers on a hand, you have disadvantage on all Saves, Checks, and Attacks made with that hand.

Spoiler: Escape Conch

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Escape Conch
Wondrous item, uncommon major item
This conch shell is cool to the touch, and anyone who presses it to their ear hears the crash of waves and the cries of seagulls.
Safe Harbor. As an action you can teleport into an extradimensional space. This space is a 10 ft. radius spiral and has the appearance of the inside of a Conch Shell. The atmosphere within is clean and pleasant, with a distinct smell of salt water.
When you activate the Escape Conch, a Medium sized conch shell that strongly resembles the Escape Conch appears in your place. This conch has AC17, 50 Hit Points, and weighs approximately 100 pounds. It is immune to Poison and Psychic damage, and has Resistance to nonmagical Bludgeoning, Slashing and Piercing damage. It automatically fails all Saving Throws. If this conch drops to 0 Hit Points you instantly reappear in its space, and any excess damage carries over to you. Additionally, you must make a DC12 Constitution Saving Throw or become Stunned until the beginning of your next turn.
While you are within the extradimensional space you have an instinctive awareness of how much more punishment the conch shell that took your place can take. While within that space, you can dismiss that shell and reappear in its place at any time. This property can't be used again until the next dawn.

Spoiler: Twincaster

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Twincaster
Wondrous item, uncommon major item (requires attunement by a spellcaster)
This small, round, unadorned hand mirror is made so that it can easily fit inside a coat pocket. By looking into it, you can cause yourself to become invisible, as if under the effects of the Greater Invisibility spell. When you do this, an illusionary copy of yourself appears in your place. The DC to see through this illusion is determined by your Spell Save DC, and unless a creature sees through this illusion they will target it instead of you. You can perceive through this copy's senses and can cast spells as if you were standing in its place. On your turn you can cause the copy to move up to 60 ft. At the beginning of your next turn the copy vanishes, and you become visible once more. This property can't be used again until the next dawn.

Spoiler: Mask of the Gloaming Court

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Mask of the Gloaming Court
Wondrous item, uncommon major item (requires attunement)
This black, silk mask is embroidered with faintly luminescent blue thread, and covers the upper half of your face. It lacks any way to stay in place, but somehow once you put it on it cannot be removed by any means unless you want it to be.
By Invitation Only. For as long as you are attuned to a Mask of the Gloaming Court, you have a standing invitation to their nightly revels.
Your Guide. When you attune to a Mask of the Gloaming Court for the first time, roll on the Animal Patron table. For as long as you are attuned to the mask it assumes the appearence of your Animal Patron, although it retains its coloration.

Roll Mask

1. Fox
2. Raven
3. Giraffe
4. Otter
5. Tiger
6. Snake
7. Owl
8. Jaguar
9. Ox
10. Rabbit
11. Frog
12. Bat

Creature of the Night. As a bonus action, you can attempt to hide in Dim Light or Darkness.

Spoiler: Aganazzar's Runekey

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Aganazzar's Runekey
Wondrous Item, very rare major item (requires attunement)
Created by the renowned sorcerer Aganazzar, this ornate, crystalline key emits a faint hum. As an action, by pressing the end of the key to your forehead and turning it, you may attempt to cast one spell that you do not know and do not have prepared without using a spell slot or material components. You cannot attempt to cast a spell of a level higher then your highest spell slot, and you cannot attempt to cast the same spell twice in a row.
In order to cast this spell you must make an Ability Check with your Spellcasting Ability Modifier. The DC for this check is equal to 10 plus the level of the spell you are attempting to cast. If you fail this check then you do not cast the spell, and instead gain one level of Exhaustion. You can use Aganazzar's Runekey a number of times equal to your Proficiency Bonus, and you regain all uses when you complete a Long Rest.

[CantigThimble]

One I came up with a while ago:
The Blood Dagger
This wickedly curved dagger has an unusual handle ringed by bladed edges. You could easily cut yourself while wielding it.
This is a +1 dagger with an activated ability. The first time it draws the blood of its weilder each day they gain the benefits of a haste spell. The dagger's design allows this to be done without expending an action and only deals one point of damage. However, the haste spell immediately ends at the end of a turn in which it does not draw blood from a new target. This causes a turn of stun the same way that a normal haste spell ending does. (Side effects of long term use of blood magic are not immediately evident from identification and are left to DM discretion.)

[Trask]

These are pretty great