For those who have not completed games in the Xenoblade Chronicles series, this page contains 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 the Xenoblade Chronicles series. As stated in Xenoblade Chronicles, Ether is the base unit of life and, without it, living beings would not be able to survive.
In Xenoblade Chronicles
Ether is needed for everything to survive on Bionis, from Zanza to Homs. The Bionis itself contains Ether within itself. After living beings of Bionis die, their body is said to "return to the Ether", which the body of the Bionis uses to produce new Ether.
Ether can be found in large pools in the Ether Mine and in the Bionis' Interior. It can also be found in Sword Valley and in Galahad Fortress in Mechonis, since the Mechon collect it both in order to weaken Bionis and use it as a lethal weapon against its inhabitants. Liquid Ether is highly dangerous, and heavily damages anything, or anyone, that falls in it.
The Monado is able to manipulate the Ether around it, resulting in the various abilities it grants its user.
In Xenoblade Chronicles X
Ether is a substance discovered by Humans shortly after their arrival to Mira. Due to its recent discovery, most of its properties are still unknown, but several weapons that take advantage of its power, as well as equipment resistant to it, were produced.
In Xenoblade Chronicles 2
Ether is the main source of energy used by Blades. In battle, Blades absorb the Ether in their surroundings and transfer it to their weapon for their Driver to attack with. However, Blades have a limit on how much Ether can be transfered before their power runs out. When a Blade uses their power, glowing Ether lines can be seen through their body.
Ether can also be find flowing through the body of the Titans, similar to blood. The colour of the Ether can be used to identify the condition of the Titan. Genbu's Ether, for example, glow with a pale, blue light, signaling its cold climate.
Ether is also used in order to manufacture several products, like Core Chips.