Enigmatic

Enigmatic Villains are characters whose origins are shrouded in mystery (or simply saying, they have an unknown past or a little information about it only). They often appear out of nowhere or have extremely vague pasts and give little clue about their identity. Their name, their true nature, or even their motives are often ignored.

Some enigmatic characters could also be heroes as much as villains.

They are often dangerous, intimidating, and unapproachable because they are unpredictable, hard to understand and (most importantly) nobody knows how to defeat them. Even when they are defeated or killed, enigmatic villains leave behind many unanswered questions. Sometimes they big bads or bigger bads that are revealed to be much worse than how the audience first predicted them as.