This version of "Laskuth the Colossus" spawns in the special Rogue Epic instanced raid. See this entry for the regular spawned version. (Note that the two are identical, except for loot.)
Spawns a chest with additional loot after a rogue at the right point in the epic 2.0 loots Miragul's Journal -- Page 191, Miragul's Journal -- Page 203, and Adventurer's Diary.