You have a +3 bonus to attack and damage rolls made with this magic weapon.

Abak-Arkng is an ancient dwemer artifact. With this gun, you can use fire salts, frost salts, or void salts with a charge to deal extra elemental damage.
Use 1 charge to deal an extra 1d12 fire damage, 1d12 cold damage, or 1d12 necrotic damage, depending on what salts are used.

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: Bonus: Magic, Damage, Combat, Range, Two-Handed, Ammunition (Firearms), Reload, Sap