Agatha's Soul Cauldron + Kiki-Jiki, Mirror Breaker + Midnight Guard

Agatha's Soul Cauldron

Kiki-Jiki, Mirror Breaker

Midnight Guard

How it works

1. Activate Midnight Guard using Kiki-Jiki's ability by tapping it, creating a token copy of itself with haste.
2. When the Midnight Guard token enters the battlefield, each other Midnight Guard you cotnrol triggers, untapping themselves.
3. Repeat.
4. You may also target any nonlegendary creature you control.

This ingenious loop turns Agatha's Soul Cauldron into a melting pot of infinite replication by feeding Kiki-Jiki, Mirror Breaker's activated ability directly onto Midnight Guard. With Kiki-Jiki's cloning powers exiled into the Cauldron and a +1/+1 counter granting those abilities to Midnight Guard, tapping the Guard creates a hasty token copy of itself. That exact entrance immediately triggers the untap ability of the original Midnight Guard, readying it to be tapped again and instantly generating an unbounded army of hasty copies.