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Morbid — At the beginning of each end step, if a creature died this turn, you may draw a card.
If a creature didn't die before a turn's end step begins, Deathreap Ritual's ability doesn't trigger at all. The creature may have died before Deathreap Ritual entered the battlefield, however.
You draw one card when the ability resolves, not one card per creature that died during the turn.
