Shirvallah, the tiger, is one of the Primal Jungle Gods in the troll pantheon. Like the other Loa, Shirvallah is held against his will.
He is represented on Azeroth through a champion of his choosing, a position formerly held by High Priest Thekal.
Judging by Zen'tabra's dialogue, he is the reason Darkspear troll druids transform into tigers. By the time of the War against the Iron Horde, troll druids had created a way for all druids to take on a half-cat form like those of Shirvallah's champions called [Claws of Shirvallah].