Persist Creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it and at least one +1/+1 counter on it due to
Bioengineered Future.
Remove a -1/-1 counter and a +1/+1 counter from that creature as a state-based action.
Resolve the
Shilgengar ability.
Repeat.
Results
Infinite artifact tokens.
Infinite Blood tokens.
Infinite creature ETB.
Infinite creature LTB.
Infinite death triggers.
Infinite creature sacrifice triggers.
Metadata
Bracket tag
OddballBracket 2-3+
Probably 2 or 3, but hard to classify
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1 · Exhibition5 · cEDH
Bracket tags are estimated from the cards and results of each combo, as a guideline rather than a strict classification.