Use Heartfire Hero's power as it last existed on the battlefield to determine how much damage it deals due to its last ability.

Valiant abilities will resolve before the spell or ability that caused them to trigger.

If a spell or ability you control has one or more of its targets changed to a creature you control with a valiant ability, that ability will trigger if that creature hasn't yet been the target of a spell or ability you control this turn.

If you create a copy of a spell on the stack and target a creature you control with a valiant ability, that ability will trigger as long as the creature hasn't yet been the target of a spell or ability you control this turn.