Form of the Werewolf

When Form of the Werewolf enters the battlefield, double your life total.
At the beginning of each upkeep, if no spells
were cast last turn, Form of the Werewolf deals 5 damage divided as you choose among any number of target creatures and/or players.
At the beginning of each upkeep, if a player cast three or more spells last turn, sacrifice Form of the Werewolf.