Cassius was inside his bathroom, splashing water on his face.
His eyes were glowing, and it wasn't from hunger or anger; it was from lust.
He wanted Rose; he wanted her in a way that might destroy the both of them if he gave in to this burning hunger for her, and it didn't help that he could smell her arousal, too.
He couldn't help acting the way he did with her when he woke up; he had heard her and Eliot's conversations, and it was safe to say that he was raving jealous.
Just as Felonious said, his body has claimed Rose as theirs; hearing something speaking to her in the manner that Eliot did made him very uncomfortable; it made him want to claim her in a way a vampire claimed his woman: fuck her and bite her.
She wasn't ready, neither was he, he knew it was just his brain playing with him through that shitty mate bond, but he didn't see himself denying those thoughts either.