Having already bolstered the heroic ranks with Batwoman, Superman and Lois Lane, it now appears that this fall’s Arrowverse crossover event has found its Big Bad.

TVLine has learned that Lost alum Jeremy Davies — who is always so excellent at playing the manically brilliant, the slightly off-kilter — has joined the three-night, Legends-less event in the role of John Deegan, a doctor at the Arkham Asylum for the Criminally Insane.

Dr. Deegan, though, just might be crazier than the inmates he treats, and as such his machinations will draw Green Arrow (played by Stephen Amell), The Flash (Grant Gustin) and Supergirl (Melissa Benoist) to Gotham City. And that, I believe, is the first indication we have had that a sizeable chunk of the crossover action (if not the final showdown) will take place on Batwoman’s home turf.

In addition to his run as Lost‘s Dr. Daniel Faraday, Davies’ previous TV credits include Justified, Sleepy Hollow, Hannibal, Constantine and an episode of American Gods.

As previously reported, this year’s Arrowverse crossover event will air Sunday, Dec. 9 through Tuesday, Dec. 11, comprised of the ninth episodes of The Flash, Arrow and Supergirl‘s new seasons. Guest stars Ruby Rose (as Batwoman/Kate Kane) Tyler Hoechlin (reprising his role as Supergirl‘s Superman/Clark Kent), Grimm‘s Elizabeth Tulloch (as Lois Lane) and Cassandra Jean Amell (as Mr. Freeze’s wife, Nora).

Want scoop on any of the above shows? Email InsideLine@tvline.com and your question may be answered via Matt’s Inside Line.