Kuudra Gatekeeper

The Kuudra Gatekeeper, Crag, lets you pick which tier of Kuudra to fight. He stands in the Forgotten Skull on the Crimson Isle and in the Dungeon Hub, and appears once you have beaten Kuudra for the first time.¹

Tiers. Your first, Basic fight is reached through Elle. Every tier after that needs the one before it beaten plus faction reputation: 1,000 for Hot (which also needs the main questline finished), 3,000 for Burning, 7,000 for Fiery and 12,000 for Infernal.¹