Breach

S1 E8: Rex wakes up in a strange place: an old boarding school with no people but a menagerie of bizarre collections and wild evos. Turns out he was grabbed by Breach and is being kept captive inside a pocket dimension of her own making. On the outside, Holiday has Breach captured and is pressing for Rex's return. Breach however has made Rex her "new favorite" and would rather see her hidden world (and all within) destroyed than to give him up.