Lancer (Fate/Grand Order - Ereshkigal)

Ereshukigaru is a Servant appearing in Fate/Grand Order.

Identity
Ereshukigaru is Ishtar's sister, a Pseudo-Servant summoned into the body of Rin Tohsaka. She is not a proper Servant, but rather considered another side of Ishtar, due to them being sister goddesses, that is summoned whenever Ishtar is summoned. She can take control of the body occasionally, but generally has no means of interacting with the world. She can take control of the underworld due to it being her domain. When fought as an enemy, she is shown being of the Lancer class, but it is unknown if that would be her proper class as a Servant.

Babylonia: The Absolute Frontline in the War Against the Demonic Beasts
Though she is initially a member of the Three Goddess Alliance opposed to Uruk, Ereshkigal takes part in the final battle against Tiamat, utilizing her Jurisdiction to weaken Tiamat and to reinforce the capabilities of the front-line combatants.