That's possible, too. But, in a show about time travel, the Trapper would be a natural fit and a huge threat.
Before seeing the idea floating around on FB, I hadn't given much thought about who Mallus might be. I guess I assumed it might be a more conventional choice of an already-established character like Zoom or Vandal Savage, perhaps. I had been preoccupied with being disappointed by the reuse of Damien Dahrk on Legends because he's one of the characters I've disliked most in the Arrowverse; plus, I almost always hate the actor who plays him any time I see him in a role. So that distracted from much contemplation of the new big bad.
If it IS the Trapper, oh, if they'd only use him (her/it?) in Supergirl and also feature the Legion in it!
BTW, in a way I didn't understand, the guys on FB think the Legion's presence on the show might relate to a secret mission to change Kara's history for the better. Other than the obvious threat of Reign, they thought the Trapper might somehow be involved if he's not being used on Legends. So I don't know know if all this is just wishful thinking on a Legion-centric FB group, but I think there may at least be something to Mallus being the trapper.
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