Urza, Lord High Artificer + Deadeye Navigator + The Ooze + Arcbound Fiend
Urza, Lord High Artificer
Deadeye Navigator
The Ooze
Arcbound Fiend
Infinite artifact ETBInfinite artifact LTBInfinite artifact sacrifice triggersInfinite artifact tokensCast all spells in your libraryExile your libraryInfinite creature ETBInfinite creature LTBInfinite blinkingInfinite blue manaInfinite creature tokensInfinite +1/+1 counters on creatures you controlInfinite Mutagen tokens
How it works
Activate Arcbound Fiend by paying 1, blinking it.
Arcbound Fiend leaves and reenters the battlefield, causing it to enter with +1/+1 counters due to its modular ability, and triggering The Ooze and Deadeye Navigator's soulbond ability.
Resolve Deadeye Navigator's trigger, repairing it and Arcbound Fiend
Resolve The Ooze's trigger, creating a Mutagen token for each +1/+1 counter that was on Arcbound Fiend when it left the battlefield.
Activate Urza's first ability twice by tapping Arcbound Fiend and a Mutagen, adding .