Only Blood Ends Your Nightmares

Oracle Text

When you set this scheme in motion, each opponent sacrifices a creature. Then each opponent who didn't sacrifice a creature discards two cards.

Card Rulings

6/15/2010 Each opponent who can sacrifice a creature must do so, and thus won’t discard any cards. Each opponent who can’t sacrifice a creature (either because they don’t control any, or because they control Tajuru Preserver) will wind up discarding two cards. Your opponents have no choice in the matter.