[Altered Backstory to fit the Ravnica Lore]

Some speak of a black-robed terrorist known only as the Reaper. His identity and motives are a mystery. What is known is that where he appears, death follows. The Reaper is an extremely volatile mercenary who used to work for the Orzhov Syndicate back in the day before being recruited by Jace and his cause.  During his time with those heroes The Reaper was heavily wounded and left for dead. He found himself under the care of a Golgari Necromancer named Moira who changed Reapers mind in regards to the direction of Ravnica and the Return of Jace Beleren. Now being Magically Altered by Moira and her secret Guild, Reaper showed no loyalty to his original cause or the organization belonging to Jace and the Heroes of Ravnica. Instead he used Jace and his group to secure intel for his new Guild "Nest" and its master Nicol Bolas. The Reaper swears to Destroy ALL Guilds.. Especially Jace and his heroes.

(His current whereabouts is unknown. Along side his Companions Moira, Widowmaker and Sombra.)

https://www.youtube.com/watch?v=X_2hsVvBPS8

This is what he sounds like ^^^