Grim Fate

After defeating the Styx Swimmer in the sewers of Undersigil, Debbie sat down to check her firearms for water damage and discovered a foot-long black and red centipede crawling up her leg. Upon killing the insect, she found it contained a small polished onyx stone with a strange symbol etched into the bottom. As she reflected on this, the creepy yet familiar voice of Lord Steelhorn whispered something only she could hear, after which she quickly pocketed the item. D&D 5e Stat Block

Ghostfoot's Catalogue of Wonders

Grim Fate

Ammunition Legendary (this item requires attunement)

This small onyx stone is carved to the size and shape of a firearm bullet. While the stone is smooth and polished, a symbol of three inverted triangles, two elongated and a hollow third nestled above, is acid etched onto the bottom. This bullet does not require blackpowder to fire. Instead, a ghostly force projects from the firearm doing bullet-like damage but the stone remains in the chamber. On a hit, the target takes 1d10 force damage and must succeed on a Wisdom saving throw (Grit DC or 8 + Dex Mod) or become cursed for 1 minute. If the target dies before the curse ends, you gain 1d6 temporary hit points. After firing, it's power remains dormant until the next dawn or if 6 Grit Points are spent. Choose a curse from the following list:

Choose one ability score. While cursed, the target has disadvantage on Ability Checks and Saving Throws made with that ability score.
While cursed, the target has disadvantage on Attack rolls against you.
While cursed, the target must make a Wisdom saving throw at the start of each of its turns. If it fails, it wastes its action that turn doing nothing.
While the target is cursed, your attacks deal an extra 1d8 necrotic damage to the target.