Mystery of the Coven

(At the beginning of your upkeep, put a research
counter on this. Counters unlock cumulative effects.)
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[0]: At the beginning of your end step, each
opponent loses 1 life and you gain 1 life.
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[3]: At the beginning of your end step, create a
1/1 black Vampire creature token with lifelink.
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[6]: {2}{b}: Each op