Enchantment, BBB (3) At the beginning of your upkeep, sacrifice Season of the Witch unless you pay 2 life. At end of turn, destroy all untapped creatures that didn't attack this turn, except for creatures that couldn't attack.1
Illus. Jesper Myrfors
Any creatures which cannot attack for some reason are exempted. [Card Text] Island Sanctuary, Moat, Arboria, and other effects or creature limitations such as the Sea Serpent's "opponent must have islands" may cause creatures to be unable to attack. [Aahz 1994/08/09]
You do not have to pay to enable a creature like a Leviathan to attack. [Aahz 1996/06/13]
You are not forced to do everything in your power to make something attack. For example, a Wall of Wonder won't be destroyed if you don't pay to animate it. [Aahz 1994/09/02] But if you do enable something to attack, and then don't, it will die.
It looks back to see which creatures could have attacked during the "declare attackers" step of the attack even if this card was not in play when the attack was declared. [WotC Rules Team 1995/11/10]
It checks at the end of every turn. [D'Angelo 1999/09/20]
Extended tournaments (see Rule 803) have banned this card since 1999/10/01.
The Dark
(Rare)