Dominion Saboteur dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it. As it enters, choose to have it copy a creature you control that has a +1/+1 counter on it, so
Dominion Saboteur will also enter with a +1/+1 counter on it.
Resolve the
Spawning Pit ability.
Repeat.
Results
Infinite charge counters on a permanent.
Infinite creature ETB.
Infinite creature LTB.
Infinite creature sacrifice triggers.
Infinite death triggers.
Metadata
Bracket tag
ExhibitionBracket 1+
For any deck
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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.