Flame Cannon (5e Equipment)
From D&D Wiki
The flame cannon is a type of cannon that has one large barrel and the ability to shot an agonizing fire from that barrel, making it a weapon that is nearly a crime to use against an enemy. Though the cannon has the ability to shot a flame in a consistent line, it does use oil and/or other flammable liquids that are consumed at a fast rate forcing you to reload it multiple times during an encounter. It also has a long line range damage with an easy ability to change the direction of fire, even while in use.
A flame cannon can fire flames in one direction using oil as ammo, it can use other flammable liquids to do the same effects. It takes two actions to load the flame cannon, one action to fire it, and a bonus actions to redirect the weapon. The weapon will continue to fire in a line for 1d4 turns before needing to reload.
Flame Breath. The flame cannon shoots flame in a 30-foot line that is 5 feet wide. Each creature in that line must make a DC 15 Dexterity saving throw, taking 10 (3d6) fire damage on a failed save, or half as much damage on a successful one.