This Servant is a limited Servant. It is only available during special summoning campaigns. When no such campaigns are active, this Servant cannot be summoned. No plans have been revealed to add this Servant to the permanent summoning pool.
Before coming here, she saved an ancient royal dynasty from a crisis, settled the internal strife of the Mankind Integration Union and routed the invaders from another Universe, but for her that is like a dessert prior to breakfast. Since they are trivial, it seems like she does not remember about them.
Until the achievement of her true, dearest wish, she shall continue to wield the Himitsucalibur. Also, no matter what, she will simply cut down the Golden Great Emperor Cosmo Gilgamesh.