Arcbound Reclaimer dies, its modular ability and persist ability trigger.
Resolve the modular trigger, putting
Arcbound Reclaimer's +1/+1 counters on another artifact creature.
Resolve the persist trigger, returning
Arcbound Reclaimer from your graveyard to the battlefield. It will not have a -1/-1 counter on it due to its modular ability.
Resolve the
Bloodthrone Vampire ability.
Repeat.
Activate
Arcbound Reclaimer by removing a +1/+1 counter from it, targeting an artifact card in your graveyard.
If needed, hold priority and repeat step 1 until
Arcbound Reclaimer dies as a state-based action due to having 0 toughness.
When
Arcbound Reclaimer dies, its persist ability triggers, returning it from your graveyard to the battlefield with two +1/+1 counters on it due to its modular ability.
Holding priority, repeat from step 1.
Results
Infinite +1/+1 counters on certain creatures.
Infinite artifact ETB.
Infinite artifact LTB.
Infinite artifact sacrifice triggers.
Infinite creature ETB.
Infinite creature LTB.
Infinite creature sacrifice triggers.
Infinite death triggers.
Infinitely large creature until end of turn.
Metadata
Bracket tag
OddballBracket 2-3+
Probably 2 or 3, but hard to classify
1
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5
1 · Exhibition5 · cEDH
Bracket tags are estimated from the cards and results of each combo, as a guideline rather than a strict classification.