Arcane Beam Cannon (Retractable)

Fitted around either forearm of the wielder upon attunement. The mixture of metal, silver, electrum, and copper line the device. On either side, where it would fit near the elbow, there are two fitted gems that glow when in use. Proficiency in firearms allows the user to add their proficiency bonus to attack rolls. The cannon has 6 charges and recharges 1d4+2 charges on a long rest. As long as the cannon has charges, it creates its own ammunition for basic attacks.

Activate: As a bonus action, the user can activate the cannon, which covers the hand of the equipped arm. That hand cannot be used to carry or interact with anything while the cannon is active. As a bonus action, the user can deactivate the cannon, which splits to fit back over the forearm, freeing the hand again.

Fire: As part of the Attack action, the user can fire a blast of arcane energy at a target, using the statistics of the Revolver from Chapter 9 of the DMG (page 267). This damage will be Force damage instead of Piercing.

Charged Shot: As an Action, the user can use up to 3 charges to fire off a charged shot. Using one charge, the attack fires a line from the user 10 feet wide and 100 feet long dealing 6d6 Force damage to each creature caught in the blast. Any creature caught in the line can make a DC 15 Dexterity Saving Throw to take half damage instead. Each additional charge adds 2d6 Force damage to the attack.

Burn Out: If all charges are used before a long rest, the cannon cannot fire until it has time to recharge, including basic Fire attacks. The next bonus action must be used to deactivate the cannon.

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: Replace Damage Type: Force, If weapon is out of charges, it cannot be used until recharged., Damage, Combat, Range, Ammunition (Firearms), Reload, Sap