Cinderhaze Wretch in exile (exiled by Agatha's Soul Cauldron).
Agatha's Soul Cauldron and Immaculate Magistrate on the battlefield.
You control at least two Elves.
Immaculate Magistrate does not have summoning sickness.
Steps
Activate Immaculate Magistrate by tapping it, putting a +1/+1 counter on it for each Elf you control.
Activate Immaculate Magistrate using Cinderhaze Wretch's second ability by putting a -1/-1 counter on it, untapping it.
Repeat.
Once you have infinite +1/+1 counters on Immaculate Magistrate, you may instead target any other creature, and you may also untap them infinitely using Cinderhaze Wretch's second ability.