For those who have not completed Xenoblade Chronicles, this page or section may contain spoilers regarding the plot. Discretion is advised.
Ether (Japanese: エーテル, Ēteru) is the building block of all life in the universe of Xenoblade Chronicles. Ether is needed for everything to survive on Bionis, from Zanza to Homs. It is said many times that Ether is the base unit of life and that without it, living beings die.
Telethia are able to absorb Ether from their surrounding environments as well as living beings like the High Entia, but that skill was only briefly displayed against Melia and her guards. The Monado is said to control the very Ether around it, and because of this, the Monado is capable of affecting all of creation. The move Monado Purge is based on Ether. Zanza completes a cycle where all the Ether is returned to him and then the world is recreated. If the cycle is not completed in time, Zanza will die. Egil decides to kill Homs to lessen the amount of Ether returned to Zanza in the cycle. The Mechon use a wound on Bionis to extract a liquid capable of dissolving all life born from Bionis.
Large pools and rivers of concentrated ether can be found in the Ether Mine, Sword Valley, Galahad Fortress, and the Bionis' Interior. Swimming in bodies of ether cause heavy damage every few seconds, making swimming in it an unwise choice.