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(An ongoing scheme remains face up until it's abandoned.)
At the beginning of your end step, you may put target creature card from an opponent's graveyard onto the battlefield under your control.
When a creature put onto the battlefield with this scheme dies, abandon this scheme.
When this scheme is abandoned, nothing happens to the rest of the creatures that were put onto the battlefield with it. They simply remain on the battlefield.
You put a creature card on the battlefield this way during the end step of each of your turns. As soon as any one of those creatures is put back into a graveyard for any reason, this scheme is abandoned.