Somnus

Somnus is an elite green drake found in the Swamp of Sorrows. He is an ancient champion of the green dragonflight. Presumably, Somnus is associated somehow with the Green Flight's purpose within the Temple of Atal'Hakkar.

He was one of the four drakes that had to be killed for the Horde side of the Onyxia-key quest chain. Emberstrife wanted Somnus' skull.

Apparently, he caused problems to lower-level players who were trying to quest in the area.

• Drops The Skull of Somnus for the quest The Test of Skulls, Somnus.

• Somnus is a Latin noun for sleep. Wiktionary