Aces High

Aces High is a legendary pistol from a different world. Gold and black filigree and small tubes flowing a white liquid in and out of it. And is possessed by a spirit. 

You gain a number of charges equal to your proficiency bonus+3, you can then use your charges on the following: 

Aces High!: you can reload this weapon, loading a single enchanted round into it, you use a number of charges into it equal to a selected items rarity, (or at dms discretion), this round then gains the effect of said enchanted item. (Example: player loads a corpse slayer round, consuming 2 charges and dealing 1d8 extra damage to undead and granting disadvantage on saving throws against turn undead) 

Blank shot: the weapon can also fire blanks, using the same rules but granting the special effect of a chosen piece of armor or wearable onto the user (bonuses to ac via +1, +2, +3 do not apply)

All out shot: the player fires a final enchanted shot, the spirit contained inside exploding out, the user takes a number of d8 necrotic damage equal to the amount of charges used in this shot and taking a point of exhaustion, however you also gain a number of d6 necrotic damage equal to charges used, also gaining the effect of a blank or aces high shot and gaining advantage on the shot. Afterwards the user must make a dc 10 constitution saving throw, falling unconscious on a fail. 

All charges to this weapon are regained at the end of a long rest. 

Additionally if someone attempts to steal or take Aces high from the attuned owner, they must make a dc 17 constitution saving throw or take 2d8 necrotic damage and, if the attuned owner wishes, can spend a charge to force another dc 17 constitution saving throw, applying a point of exhaustion on a failure. 

To attune to the aces high, the player must use 3 long rests, wherein instead of resting, he sits and speaks with the spirit within this weapon, the player must succeed on a dc 16 charisma (persuasion) check, then a dc 12 constitution saving throw, or take 2d8 necrotic and fail this attunement step, however they do not lose their progress. 

It’s up to you to decide whether a character has proficiency with a firearm. Characters in most D&D worlds wouldn’t have such proficiency. During their downtime, characters can use the training rules in the Player’s Handbook to acquire proficiency, assuming that they have enough ammunition to keep the weapons working while mastering their use.

Notes: Weapon Property: Loading, Bonus: Magic, See below., Range, Ammunition (Firearms), Reload