The Doomcannon's primary ability is automatic shotgun fire. 40 Energy is used per second to fire 7 red plasma projectiles, called "doom shot," once every 0.9 seconds (approx. 1.1 shots per second) with a damage per second of 17.5 before armor multipliers. The pieces of shot deal 20 knockback (average knockback power) to enemies they hit.
The Doomcannon's alt ability is a special grenade launcher which consumes 40 energy per use to launch a Doom Grenade. This ability differs from the Grenade Launcher ability sometimes possessed by generated Shotguns, Assault Rifles or Sniper Rifles though. It deals absolutely no damage, just inflicts the Doomed debuff to all enemies hit.
Both abilities inflict the Doomed status effect on enemies. This special status effect lasts for 7 seconds and causes an explosion centered on the victim if they take a total of 10 damage starting 0.1 seconds after the effect begins. This explosion deals 130 defense-ignoring damage, which can be further enhanced via armor damage bonuses or the Rage buff.
- A good tactic for the Doomcannon is to carry around a secondary weapon that deals a large amount of damage in a single attack, such as Tesla's Wrath or the Vintage Scoped Rifle, to trigger the Doomed debuff's explosion. While a follow-up shot from the Doomcannon's primary fire can trigger it, this can typically only be done at close range due to the weapon's spread.
- The secondary fire's grenade deals no damage (only inflictis the Doomed debuff) and might only be good to "predebuff" enemies from the safety of some small cover using the fact that grenade's trajectory is affected by gravity. In a direct fight the primary fire should be used instead whenever possible.
The Doomcannon's sprite is inspired by the BFG from the original DOOM game, as it can be clearly seen on this picture.