Harry Lloyd has been cast as Professor X in the Shadow King.

Legion is loosely inspired by the X-Men comics, where David Haller is the son of the X-Men's founder Charles Xavier and his lover Gabrielle. Gabrielle kept David's very existence a secret from his father for years, and Xavier was shaken to the core when he realized that his son possessed both almost unlimited power and serious mental instability. In the comics, each of Legion's different personas can tap into a different superhuman ability, and some of them are very dangerous indeed.

Related: Legion Season 3 Casts Lauren Tsai as Mutant Named Switch

Although David's personal history has been subtly rewritten for the small screen, the series has been teasing Professor X for quite some time. Now Legion's Twitter has officially confirmed that both Charles Xavier and Gabrielle Haller have been cast for guest roles in season 3. Harry Lloyd (Marcella, Hang Ups, Counterpart) will be playing Charles Xavier, while Stephanie Corneliussen (Mr. Robot, Deception) will be stepping in as Gabrielle Haller. The tweet describes these as "guest casting," suggesting they won't have a major role, and indeed may only play a brief cameo.

Legion FX

Legion is one of two Marvel TV series produced by a partnership between Marvel Television and Fox. This is actually the first time any of the major X-Men will appear in one of these TV shows; in fact, Patrick Stewart to cameo, but it seems Hawley has instead gone for recasting the role.

It's been confirmed that Legion season 3 will bring the series to an end, in accordance with Hawley's plans all along. Hopefully this latest news means that Legion will ultimately bring David face-to-face with his long-absent parents, rather than simply featuring them in a flashback scene of some kind. That would be a fitting end for David's story, as he finally finds the family he's always longed for.

Source: Legion