Lorthos was a monstrous octopus who lived in the oceans of Zendikar. The merfolk of the plane believed he controlled the tide. Many adventurers were fearful of Lorthos because of countless tales told by sailors and treasure hunters who have barely escaped his deadly grasp. The creature was often seen in the Sunder Bay region of Murasa in the same proximity as the Joraga nation leader Speaker Sutina. Any connection between the two is unknown.
Lorthos was summoned by Kiora in an attempt to retake Sea Gate from Ulamog's brood of Eldrazi, and was ridden into battle by her and several other merfolk she had brought with her. However, upon reaching the city, they were faced with not one, but two Eldrazi titans: Ob Nixilis had summoned Kozilek from underneath Zendikar. As they both saw each other as threats due to their immense sizes, they began to battle; however, this fight did not last long, as the titan destroyed Lorthos by slicing it in half using its arm blades.