"And has it occurred to you that simply spending so much time near a true fae is what causes the change to begin?" Childermass counters just as viciously, treating Strange like he's just as stupid as Strange seems to think the changeling is. "You'll be useful until you change too much, then I'm sure she'll find a lovely cage to stick you in for laughs."

To be fair, brainwashed can be reversed. Strange will be lucky to get out of here without poisonous plants sprouting from his hair.