Combat Cannon [Written]

[Thomas★Zero]

Combat Cannon
Continuous Trap Card
During either players Battle Phase, you can activate this card from your hand. Each time at the start of the damage step, when a monster you controls battles an opponents monster: Inflict 400 points of damage to your opponent. You can only control 1 face-up "Combat Cannon".

So Combat Cannon is a continuous burn card focused on dealing damage each time a monster you control battles an opponents monster where it can be sprung during either players battle phase which allows you to effectively play it going first or second where its balanced by having you only be able to control 1 face-up combat cannon while it does 400 for each battle that occurs.