Arsenal of Dhebisu - Ranged (lightning gun)

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

Once on your turn, while you are wielding this rock you can transform it into any weapon of Small, Medium, or Large size—melee or ranged, one-handed or two-handed, simple or martial. If you release it for more than a minute, it reverts to being a (brilliantly-glowing) rock.

If just transformed into the form of a melee piercing weapon, it deals extra 2d6 fire damage on the first attack.

If just transformed into the form of a melee slashing weapon, and you make an attack this turn, you go into a defensive stance. Until the start of your next turn, you may use your reaction to parry a melee attack and use the result of the first attack as your AC. 

If just transformed into the form of a melee bludgeoning weapon,  after the first successful attack you can use your bonus action to make an opposed Strength (Athletics) check to try to push the target. You have advantage on the check. If you succeed by 5 or more, they fall prone.

If just transformed into the form of a ranged weapon that uses missiles or bullets, it deals an extra 2d6 fire damage on the first attack. It also never runs out of ammunition.

If just transformed into the form of a thrown weapon, it ignores all cover less than full cover and returns to your hand immediately after being thrown.

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, Replace Damage Type: Lightning, Proficiency: Firearms, Range, Ammunition (Firearms), Reload, Sap