"Hurt us, hurt 'em more. Simple?"
Perhaps a mistranslation of the demon word for 'Spine' or simply an apt name for a weapon that feeds off spiteful desire to enact the user's will. This rifle is a long one, it's barrel all the way to the stock is formed of vertebrae. The Spinus Process form the iron sights, the tail bones are the butt stock, and the rib cage is the body of the gun. Wrapped and weaved throughout the bones are black veins which lie dormant.
To shoot the gun, conventional ammunition is not needed. Simply choose the damage die (or dice) you wish to use (d4, d6, d8, d10, d12, or 1d20) and add half of the dice value.
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.
This weapon has the following mastery property. To use this property, you must have a feature that lets you use it.
Slow. If you hit a creature with this weapon and deal damage to it, you can reduce its Speed by 10 feet until the start of your next turn. If the creature is hit more than once by weapons that have this property, the Speed reduction doesn’t exceed 10 feet.
Notes: process to create the item, binding it to the creator and none else, Range, Two-Handed, Ammunition (Firearms), Reload, Slow