ya girl is back at it again with another (probably) poorly written homebrew item! your pyromaniac artificer loose an arm? well this is the item for them! for the cost of an arm, a little sanity, and about a day of your time, you too can set shit on fire and pretend to be smart while doing it

Alchemist’s prosthetic:

• A large, bulky, brass prosthetic left forearm, covered in elaborate detail work, as well as an out of place collection of various alchemical symbols, arranged into a sort of equation, seeming to have been meticulously scratched into the metal with a blade. When deciphered, this equation is revealed to be the recipe for making alchemist’s fire, a volatile and highly flammable liquid
• Requires the replacement of the left arm
• 10ft cone centered on the user, 1d6F, sets target on fire (1d4) for three rounds or until the victim is extinguished 
• can be used as a reaction with a successful dc14 dex save
• The arm has three charges, which can be restored as a bonus action in combat with alchemist’s fire flasks. One flask restores a single charge
• The arm also comes with a large container with which to reload the arm. It can be filled with three flasks of alchemist’s fire. While the container cannot be filled during combat, a full container can be loaded into the arm as a bonus action, restoring all three charges
• The arm requires constant cleaning, requiring a dc12 int check with a set of blacksmith’s tools. 
• if not cleaned for two days, initial damage is reduced to 1d4
• After four days, the user will take 2 fire damage each time the arm is fired
• After a week without cleaning, the arm has a 20% chance to explode upon being fired, increasing by 5% each time it is fired. Percentage resets to 20% if the arm is not fired for an hour. Cleaning dc increased to 15
• Percentage permanently increases by 5% for each additional week it is neglected
• If the explosion chance reaches 100% the arm no longer functions and must be repaired. Repair costs 180 gold, as well as materials, and takes four hours to do. This requires a dc 17 int check with a set of blacksmith’s tools. This also goes into effect if the arm explodes at any time during use, either by neglect or overloading (if applicable) 

Optional variant rule:

• Overloading
• The arm functions on a system similar to a gas powered airsoft gun, where the canister is inserted and a small pin breaks the seal, allowing the pressurized contents to enter the internal canister, where they remain until needed. This can be taken advantage of to store an extra three charges, as long as the bolt is not fully closed. Overloading the arm by driving the bolt home with an additional full canister increases the initial damage to 1d10 and burn damage to 1d6, but has a 15% chance of exploding when fired. When an overloaded arm is fired, it expends all stored charges at once. Dm may determine the effect of attempting this with a partially full canister/arm

as usual, criticism is welcome and, if you feel so inclined, you are more than welcome to use this item in your game! i can do my best to answer any questions about this item, though replies may be very slow lol