Armcannon

During the twilight years of the Last War, House Cannith equipped experimental Warforged units with arm-mounted variants of the force ballista. Though lacking the punch and range of their larger cousins, they were nonetheless effective as a sidearm for skirmishers and scout units.

An armcannon is a magic weapon that attaches to your arm, becoming inseparable from you as long as you’re attuned to it. To attune to this item, you must hold it against your forearm for the entire attunement period. It uses the stats of a hand crossbow and benefits from features that apply to such weapons, except that it deals force damage instead of piercing damage and it requires no ammunition.

As a bonus action, you can retract the armcannon into your forearm or extend it from there. While it is extended, you can use the weapon as if you were holding it, and you can't use that hand for other purposes.

The armcannon has 1 charge. When you make a ranged attack using this weapon, you may expend a charge. If the attack hits, you deal an additional 2d6 force damage. The armcannon regains 1 charge when an Eberron Dragonshard is applied to it (no action required).

Soulbound Variant (Very Rare)

At the DM's discretion, some armcannons have the following additional properties:

• You have a bonus to attack and damage rolls with this magic weapon equal to one fifth of your character level (rounded down).
• You cannot voluntarily end your attunement to this magic item except with the help of a powerful artificer. If your attunement to this item ends, you cannot attune to it again. 

Proficiency with a Hand Crossbow allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Replace Damage Type: Force, Damage: Force, Warforged, Ammunition, Light, Loading, Range, Vex