エンチャント
各プレイヤーのアップキープの開始時に、そのプレイヤーは土地でもトークンでもないパーマネント1つを生け贄に捧げる。そのプレイヤーがそうできないなら、そのプレイヤーはカード1枚を捨て、そのプレイヤーは2点のライフを失い、あなたはカードを1枚引き、あなたは2点のライフを得て、あなたは警戒を持つ白の2/2の騎士・クリーチャー・トークンを1体生成し、その後あなたは予言された壊滅を生け贄に捧げる。
If Doom Foretold leaves the battlefield or changes control while its ability is on the stack, its effect still happens. You just won't be able to sacrifice it if instructed to do so.
If the player can sacrifice a nonland, nontoken permanent, that player must do so. They can't choose to rush toward their doom.
During your upkeep, you can sacrifice Doom Foretold for its own ability.
If the player is unable to sacrifice a permanent and is unable to discard a card, they still lose 2 life, and the rest of Doom Foretold's effects happen.
In a Two-Headed Giant game, Doom Foretold's ability triggers twice during a team's upkeep. In any order you'd like, each of those players has to sacrifice a permanent. The full consequences happen if that player can't, even if you sacrifice Doom Foretold as the first triggered ability is resolving.