Siren's Call

It will require creatures with Haste to attack since they are able, but it won’t destroy them if they don’t for some reason.

The creature is destroyed if it does not attack because it simply can’t do so legally.

This will destroy creatures that weren’t able to attack because they had been previously tapped.

If a turn has multiple combat phases, this spell can only be cast before the beginning of the Declare Attackers Step of the first combat phase in that turn.