Fyrus

Fyrus is the boss of the Goron Mines.

Fyrus is Darbus' infected form when the fused shadow took over his body. Due to his ferocity and inability to control himself as well as causing menace, the Goron elders locked him away deep inside the mines. As with most bosses in the Zelda series, you must first make Fyrus vulnerable and then attack his weak point repeatedly to defeat him. To do this, you will need your Hero's Bow and the Iron Boots. First, attack the glowing jewel on his head with an arrow. This will temporarily distract him and give you the time you need to knock him over. Equip the Iron Boots and grab the end of one of the chains attached to his legs and pull. This will cause Fyrus to fall over. Quickly run to the front of the large creature and repeatedly attack the jewel on his forehead with your sword. Repeat the process until he is defeated. Once Fyrus is defeated, however, the twilight matter from his altered form fuses into a singularity, creating the second Fused Shadow. Link is able to look upon a confused Darbus, as the Goron shows himself, unable to realize what had happened to him thus far. Link is also awarded a heart container for his efforts.

Trivia

 * Fyrus was the first ever boss revealed for Twilight Princess. He was present in the first trailer for the game.