"Revenant Wings" also introduced beings known as the "Yarhi". Also known as "Espers" to those on Ivalice, they are powerful entities created from anima, spiritual energy. Through certain elements, such as Auracite or Mist, the Yarhi can assume physical form until they are defeated in battle. They are summoned by the wielders of Auracite and obey their every command. Fourteen such Yarhi appeared in "Final Fantasy XII"; the first thirteen being the Lucavi from "Final Fantasy Tactics" which are referred as the "Scions of darkness", magical beings created by Occuria with great strength and intelligence. Led by Ultima, they eventually rebelled for various reasons and engaged themselves in a war dubbed the Thousand Year War against the gods; but they were eventually defeated. Consequently, the gods bound their existence with the Glyph of the Beast, trapping them within the Mist. Any who controls the Glyph in turn controls the Scion, allowing them to operate as summoned creatures. The Fourteenth is the legendary swordsman Gilgamesh, who collects the swords of those he defeats in battle. While most fight, few like Cu Sith and the Sahaguin Namingway offer aid in other ways. Also, the viera job "Summoner" can call and use the powers of mythological gods like Kirin, Shiva, and many others.