The Strain's Jack Kesy has been cast as "Black Tom" Cassidy for 20th Century Fox's Deadpool sequel, according to Deadline. Cassidy is described as a "major villain" for the film, but Josh Brolin's Cable is the "principal" villain according to the Hollywood trade.
"Black Tom" Cassidy has fought Deadpool numerous times in comic books, including in the first Deadpool miniseries, 1994's Deadpool: The Circle Chase. In comic books, the Irish villain is Banshee's cousin - and secretly raised his daughter, Siryn. He is known to work with Juggernaut extensively, and while none of these other characters have been reported as being part of Deadpool 2, all three have appeared in Fox's X-Men movies.
Kesy is best known for playing the Master in FX's The Strain, and also appears in this month's Baywatch.
The as-yet-untitled Deadpool sequel is scheduled for release June 1, 2018.