Towering at 6ft 8in, the former NFL star will play Lash, an Inhuman who "has a fairly strong opinion about what should happen to Inhumans", according to executive producer Jeff Bell, reported Access Hollywood.
Following the second season finale, Inhumans are now "popping up all over the world".
"What's nice about him is he's a wild card. You don't know why he is doing this. Does he have an agenda? Is he on somebody's side? So we'll be teasing that out over some episodes."
"We worked with Glenn Hetrick (The Hunger Games), who we worked with last year on Raina, and he and his team do great work," Bell added.
Willig has previously appeared in "Brooklyn Nine-Nine","Grimm", "NCIS" and "Chuck".
Meanwhile, Blair Underwood has been confirmed to be returning as Andrew Garner in the third season of the superhero drama.