Soul of Fire, and 20 Fire Shards at a Tinkerer's Workshop. This accessory is required in the Kinetic Boots recipe, and the effect is given as the bonus of the Caesium Armor set.
|Lava Merfolk form.|
Bullseye55's 1.2 Dev Notes: Attainable at the end of the revamped Hellcastle dungeon, which is at the end of Hardmode. Found in a Hellfire Chest.