Ishtar

A goddess of beauty, good harvests and war from Mesopotamian mythology. Said to be the most pampered, or rather, most beloved goddess by the other deities. This form is not that of the goddess Ishtar herself, but a pseudo-Servant condition in which a human that has a wavelength close to her own was made into a vessel. She says that her role is to watch over humans in a way appropriate for a goddess, but that means to watch over while snickering.

(Source: Type-Moon Wiki)