Bloodthorn Lair is an Ayleid Ruin on the island of Betnikh. Here the Bloodthorn Cult have their lair and one of the quests in The Bloodthorn Plot leads the Vestige to this location. There are several entrances to the ruin.
This quest is one of three quests within The Bloodthorn Plot quest one must complete to proceed. Laganakh senses evil spreading on Betnikh and the need to know what's facing them before fighting, a use of a totem can bring up visions that might be of help.