The Moon Eating Serpent
I'll explain again. In the Age of Gods, the Bakunawa was a beautiful goddess who loved the moon. He was a great serpent that devoured six of the seven moons. It died at the hands of Thaya. During the Far War it was a horrible weapon that almost destroyed our world. It shattered the moon. Thaya killed it again. It became the great moon tree Lokorn. Easy to understand, right!
It returned as a weapon of the Far Realm during the War Against the Far Realm. They sent it to break open Erathia and awaken the Sleeper. The monster was diverted and it redirected itself to the last object of it's lunar hunger. Thaya killed it again, but at the cost of her life and both of their bodies fell to the surface of a now Shattered Moon.
The forces of the Far Realm used its corpse as a source of power and raw materials for their armies that invaded Erathia. In a turning point in the Far War, its body was transformed into the great balete tree Lokorn.