I expect it to not work but would it be possible to use Dark Charm for movement, interrupt the movement to maintain the monster status for the hero (I think you can interrupt movement voluntarily while you can not do that with an attack action) and use call of the raven on it? Both cards are used during start of the turn, but would a charm hero even be a valid target for COTR? The card says he can move / attack as one of your monsters but not mentions if it is considered a monster for other effects.
COTR: Exhaust this card at the start of your turn and choose 1 monster. Place 1 Raven Flock Servant token in a space adjacent to that monster. Then, that monster suffers 4 Heart.
Dark Charm: Play this card on a hero at the start of your turn. The hero tests Willpower. If he passes, draw 1 Overlord Card. If he fails, you may perform a move or attack action with that hero as if he were one of your monsters this turn. You cannot force him to suffer Fatigue or use a Potion, but you may force him to attack himself.