Grigori Rasputin

The master of gacha
Alter Ego (アルターエゴ, Arutā Ego) is an Alter Ego-class Servant working as one of the three Alter Ego apostles of the Alien God in the Lostbelts of Fate/Grand Order: Cosmos in the Lostbelt. They are working in tangent with the seven Crypters attempting to supplant the Greater History of Man with the Lostbelts. He first appears under the name Kirei Kotomine (言峰 綺礼, Kotomine Kirei), acting as an a Executor from the Church tasked with overseeing the investigation into the dissolution of the previous staff of Chaldea for the incoming director Goldolf Musik.

Alter Ego's True Name is Grigori Rasputin (グリゴリー・ラスプーチン, Gurigorī Rasupūchin),  known as the monster responsible for the Romanov Dynasty's collapse. He is a Pseudo-Servant in the human corpse of Kirei Kotomine, who died in Japan in around 2004.

The Slow Rumble
Grigori was summoned alongside Gilgamesh thanks Nomura using to the mammon machine, but for what purpose the Mad Monk had been brought from the Throne of Heroes?