Each of your Characters gets "Retreat this unt Prevent up to 4 damage to this unit, and it gets Backfire 2 (if you roll at least one natural 3 for this attack, this unit does 2 dice of damage to itself when the attack ends.) until it is discarded."
Keywords
Backfire
Backfire X: A cumulative ability triggered by the initial dice roll that means, "When you roll at least one natural three with this unit's attack dice before re-roll, this unit does X dice of damage to itself when the attack ends." Backfire applies only to dice rolled for an attack, not to dice rolls for abilities like Retaliate.