Skill.
Uses (3 warrior counters). Max 1 per player.
Interrupt: When your hero attacks, remove 1 counter from here → that attack deals 1 additional damage.
Best with attacks that deal their damage to multiple targets: Dive Bomb is the prime example, but other good cases like Melee and Ricochet Beam exist.
Note that this increases damage of one attack. Things that are explicitly multiple attacks, such as Dance of Death or Slice and Dice do not synergize well with this.
On paper this card gives you 3 damage, spread out across three separate attacks, for 3ER. 3 damage for 3ER isn't too amazing, but I think there's real value in allowing you to assign damage more efficiently. For example, you can spend a use to get an extra card out of No Quarter or to one-shot one of the Sinister Six with Relentless Assault.
Can this effect be use with domino's pistols so it can make 2 damages for each resources? And where can I find the specific on when It would be valid and when it wouldn't