Isis is Catwoman's pet.
Biography
Catwoman is shown to keep many cats, among those is Isis.
Events in Injustice
Isis is shown during Catwoman's intro, taking a diamond from her and bringing it to the thief's lair. She is also playable in a S.T.A.R. Labs Mission, during which she has to sneak into Gotham City's Museum to collect data on the location of Batman's hidden lair.
Isis also appears in Injustice 2, summoned by Catwoman during one of her attacks.
