Hyouma Sagara

Hyouma Sagara is a magus and original Master of Assassin in the prototype short story version of Fate/Apocrypha Act1: Unbirth. He is mentioned to have been the one to summon Assassin in a similar manner in the novel version of Fate/Apocrypha.

Little is known about Sagara's background, but it is known that before becoming a master he was born from a lineage of magi that was commonly looked down upon as "rats". Before the Great Holy Grail War, he was living with a prostitute by the name of Reika Rikudou, who was unaware of the existence of Magecraft, and at some point in time he managed to gain possession of Jack the Ripper's knives.

In Fate/Strange Fake:

During the True and False Holy Grail Wars, he and many other magi attempt to attack Flat Escardos to get his Command Seals, only to be easily defeated by him and False Berserker. Flat temporarily paralyzes and seals the Magic Circuits of himself, Carl Lexarm, Silvelt Kotcheff, Avi Dikhail, and members of Zugzwang before locking them in his room. When False Berserker unwittingly takes the form of Assassin of Black, he and the other prisoners instinctively shudder in fear much to their own surprise. When Flat refuses to kill them, he and the other prisoners are confused. Flat and False Berserker leave them in the room.