Cast Chain of Smog by paying {1}{B}, targeting yourself.
Quandrix Pledgemage triggers, putting a +1/+1 counter on it.
Resolve Chain of Smog, causing you to discard two cards and copy Chain of Smog, targeting yourself.
Repeat from step 2.

Infinite +1/+1 counters on Quandrix Pledgemage

Infinite magecraft triggers

Chain of Smog

Quandrix Pledgemage

Cast Chain of Acid by paying {3}{G}, targeting an indestructible noncreature permanent you control.
Quandrix Pledgemage triggers, putting a +1/+1 counter on it.
Resolve Chain of Acid, destroying nothing and causing you to copy Chain of Acid, targeting an indestructible noncreature permanent you control.
Repeat from step 2.

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