It is later revealed that Goku Black's true identity is, an apprentice from Universe 10, who hijacked Goku's body from an unaltered timeline as part of his plan to attain immortality and wipe out all mortals.
It is later revealed that Goku Black is the future self of, an apprentice from Universe 10. In the anime's original timeline, Zamasu hijacked Goku's body from an unaltered timeline as part of his plan to attain supreme power and wipe out all mortals.