Siren's Call

An attempt to give blue a combat trick built on compulsion rather than denial: the spell forces the active player's creatures into the red zone, then threatens to wipe the ones that stayed home. Two pieces of friction sit at its core. First, it has to be cast on the opponent's turn before attackers are declared, which means it lives in a tiny pre-combat window most players have no reason to pass priority in. Second, the punishment clause carves out walls and creatures that changed hands mid-turn, which betrays how much the original rules team worried about edge cases (token armies, stolen creatures, defenders held back as chump blockers) breaking the symmetry. The result reads like a riddle and plays like a bluff: the threat of Siren's Call mattered more than its resolution, because a savvy opponent simply attacks with everything and loses nothing, since attackers are exempt from the end-step sweep. It sits among a cluster of early blue cards that tried to express the color's identity through "must attack" coercion rather than countermagic, a design lane Wizards eventually abandoned once they decided blue's wheelhouse was telling you what you couldn't do rather than what you had to.