Fiend Fire

Fiend Fire is a 2-Energy Ironclad rare attack that exhausts your entire hand and deals 7 damage per card exhausted (10 per card upgraded). If you have 5 cards in hand when you play it, Fiend Fire deals 35 damage for 2 Energy. With a full 7-card hand, that's 49 damage — far more than any other 2-Energy attack. The Exhaust means all those cards are gone from this combat, but the burst damage output is among the highest in the game.

Fiend Fire is a powerful finisher that works best when you have a large hand size (Runic Pyramid, Battle Trance) and expendable cards that won't be missed (Wounds, curses, basic Strikes). Pairing with Headbutt lets you save one important card from the Exhaust by recycling it first. Upgraded at 10 per card, the potential damage becomes absurd. It's one of the Ironclad's strongest burst win conditions.