This weapon scales with your Gunslinger level, and the abilities of the weapon are not all immediately available.

Magical Weapon. Starting at level 5 the weapon gains a +1 bonus to attack and damage rolls, at level 10 the bonus increases to +2 and the Firefly ability is unlocked, and at level 15 the bonus increases to +3 and the Momento Mori ability is unlocked and gains 6 charges for use with the ability.

Firefly. Whenever you kill a creature with equal to or more hit dice than you, roll a D20. On a 20 the dying creature explodes in a fiery inferno and you gain back one grit point, creatures within a 10 foot radius of that creature must make a DC15 Dexterity saving throw. A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one. Once this effect successfully triggers you must complete a short rest before it may trigger again.

Momento Mori. Whenever you kill a creature, you may use your bonus action and expend one of the weapons charges to quickly load a special round into the Ace of Spades. If you already can reload the weapon as a bonus action you may instead load it as part of the attack. Your next attack with the weapon deals a bonus 2d10 force damage. You regain all charges for this ability after completing a long rest.

"Folding was never an option." —Cayde-6

 

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: Momento Mori, Gunslinger., Range, Ammunition (Firearms), Reload

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: Damage: Piercing, Requires attunement by Gunslinger, Range, Ammunition (Firearms), Reload, Sap