Bargain Chamber

 A chamber that contains viscous elemental explosives that is attachable to a firearm. It can be attached a number of times equal to your proficiency bonus (+3) and lasts 1 minute. All charges recharge daily.

Once attached, the chamber gains one of the following damage types (roll on the damage type table). It does 1d8 additional damage to the target. On a natural 20 the damage die increases to the next damage die (max of a d12), and on a natural 1 the damage die is reduced to the previous die (min of a d4) for the duration.

The color of the viscous material will correspond with the type of damage rolled. 

Color Reference:

Notes: Damage: Acid, Damage: Cold, Damage: Fire, Damage: Force, Damage: Lightning, Damage: Necrotic, Damage: Poison, Damage: Psychic, Damage: Radiant, Damage: Thunder, Damage, Buff, Artificer