Annihilation

This massive, 50 pound beast of a weapon is lit with a mysterious green aura. When fired, the aura briefly grows brighter and the gun shakes violently. Made of blackened mizzium, this weapon is unlike any other. The guns intricate machinery hisses and clicks with clockwork-like regularity.

This gun has a misfire score of 7, and has no reload property. After it has been fired, it cannot be done so again until the creature attuned to it completes a short or long rest.

You gain a +3 bonus to attack and damage rolls made with this weapon, which deals radiant damage instead of necrotic damage.

When a creature is shot with this weapon, they cannot take reactions until the end of your next turn and must make a DC 17 Constitution saving throw or be paralyzed until the end of your next turn.

In addition, when you attack a creature with this weapon and roll a 20 on the attack roll, if that target has less than 50 hit points (after taking the damage of the attack), that target must make a DC 17 Constitution saving throw or be instantly vaporized. A vaporized creature and everything it is wearing and carrying, except magic items, diffuses through air in a matter of moments. The creature can be restored to life only by means of a true resurrection or a wish spell.

While holding this weapon, you have advantage on Charisma (Intimidation) checks as well as immunity to the frightened condition.

When this gun misfires, an explosion of intense radiant energy rapidly expands out from the gun. All creatures within 20 feet of the gun when it explodes must make a DC 17 Constitution saving throw. A target takes 15d8 radiant damage on a failed save, or half as much damage on a successful one. If the gun explodes in this way it must be repaired in a workshop with the proper materials. The Tinker's Tools check DC to repair the weapon is 24. It takes 12 hours of work and 2000 credits to do so.

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, Advantage: Intimidation, Immunity: Frightened, Replace Damage Type: Radiant, Damage, Combat, Range, Two-Handed, Ammunition (Firearms), Reload, Sap