Cherubim is the code name of an assasin and Immortal . She is the Oldest of the Immorals
a winged angelic being described in biblical tradition as attending on God. It is represented in ancient Middle Eastern art as a lion or bull with eagles' wings and a human face, and regarded in traditional Christian angelology as an angel of the second highest order of the ninefold celestial hierarchy.
In some legends an angel so named was placed as a guardian before the gates of paradise, wielding a sword able to split the world.
It is also unclear if there is a group of such entities or if there is just one.
It is unclear but it is assumed that the Immortal mystery being calling herself Cherubim, has some sort of connection to this legend. She guards Earth (Paradise) and some say she has access to a world consuming weapon, a weapon that is not of Union or any known origin. She used this weapon once.