I don't know if its a demon or a devil... or just some hungry thing from some dark place in time... I just know that it's not gonna stop coming after you, or anyone else it wants to. Once it has the scent of something it likes... It can't, it can't stop.
~ Jezelle Hartman
Zamasu and Goku Black were far too different for us to conclude that they were the same being. What we felt from Goku Black was an immense evil Ki. But Zamasu didn't have that level of evil in him. Furthermore, Zamasu did not know Goku, but Goku Black spoke as if he did know him.
~ The mystery between Zamasu and Goku Black

Enigmatic Villains are characters who are surrounded in mystery. They often appear out of nowhere or have extremely vague pasts, and give little clue about their identity. You ignore their name, their true nature, or even their motives.

They are also very dangerous, intimidating, and unapproachable, because they are unpredictable, hard to understand and (most important) anybody does not know how to defeat them. Even when they are stopped, Enigmatic Villains leave behind many unanswered questions.