A pale mutant who can feel where other mutants are, which makes him useful to people he would rather not be useful to.
Caliban is a mutant with chalk-white skin and the ability to locate other mutants, and two films use him for opposite things. Tómas Lemarquis plays him in X-Men: Apocalypse, set in 1983, as an underground broker who tracks mutants for money. Psylocke is his bodyguard until Apocalypse recruits her. The reader who sent this list wondered what he was doing in the eighties; the answer is that this is his first appearance, and the second is nearly fifty years later in the story.
In Logan, set in 2029, Stephen Merchant plays him as a friend of Logan and Professor X, living with them in the future with a severe sensitivity to sunlight. Logan drives a limousine; somebody has to stay home with the old man, and that is him.
Minor spoiler
He is abducted by the Reavers to track Wolverine for them, and he does it, under duress, until he kills himself with grenades rather than go on.