Alchemist's Flamethrower

"A steel contraption with a heavy fabric glove.  It takes the form of a armmounted canon with a long holow rod at its front end. A small door in its central body can be opened, there a small glas bottle can snuggly fit."

You can load a small glas bottle with about 500ml or less of liquid into the small compartment, as part of an attack action you may use the device to spray the liquid in a 10 ft cone in front of you. Loading a bottle takes an action. You can load vials as a bonus action. 

As part of an attack action, you may fore go an attack to force every creature within the area of effect to make a DC14 dexterity saving throw . On a fail, they become subject to the following effect in dependence of the liquid in its compartment:

• Alchemist's Fire:  Every creature takes 4d4 fire damage. In addition the next attack deals an aditional 1d4 fire damage.
• Acid:  Every creature takes 2d4 acid damage.
• Holy Water:  Every undead creature takes 4d4 radiant damage and must make a wisdom saving throw. On a fail they are frightened.
• Oil:  The area and every creature within are covered in oil and take 5 fire damage if it catches on fire. In addition every creature moving through the area must succed a DC12 dexterity saving throw or become prone.

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

Notes: Weapon Property: Loading, Weapon Property: Heavy, Sap