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.

Infinite magecraft triggers

Infinite +1/+1 counters on a creature

Chain of Acid

Quandrix Pledgemage

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.

Combos with "Quandrix Pledgemage"