Before the start of Xenoblade Chronicles, Bionis attacked Mechonis to destroy the Machina and then engage in a battle with the mechanical titan. During the battle, Mechonis loose its left arm and Bionis takes a huge hit on his right flank. Bionis' weapon, the Monado, is then retrieved by the High Entia and sealed away in Ose Tower to prevent the Bionis' reawakening.
The Bionis reawakens later, when Zanza exits Shulk's body and returns to controling the Bionis' actions. He destroys Mechonis and then attempts to destroy all life on Bionis in order to recreate the universe.
Bionis collapses after the final battle with Zanza since Shulk wished for a world with no gods. Its remains are present in the sea around Colony 9 in the new universe created by Alvis.
Bionis appears as a part of the Gaur Plain stage since it is located on its leg as well as a Trophy exclusive to the Wii U version.
The region known as Bionis' Leg is a vast landscape of lush fields, towering hills, and flowing rivers. But its name is no metaphor. No, it really is the leg of the titanic Bionis, a god whose body has become an entire world since it fell in the battle long ago. Whole races, such as Homs and High Entia, have lived and died on this great being.
Bionis can be considered Male due to the fact that Zanza, Bionis' soul is male in the same way that Meyneth, Mechonis' soul is female