Agatha's Soul Cauldron + Inquisitive Puppet + Metallic Mimic

Agatha's Soul Cauldron

Inquisitive Puppet

Metallic Mimic

How it works

1. Activate another creature you control that has a +1/+1 counter on it by exiling it, creating a 1/1 Human creature token that enters the battlefield with a +1/+1 counter on it due to Metallic Mimic.
2. Repeat using the Human token instead.

This clever loop uses Agatha's Soul Cauldron to grant an activated ability to your creatures, drawing on a self-referential cycle of sacrifice and rebirth. By exiling Inquisitive Puppet, you gain the ability to cash in your creatures for 1/1 tokens; thanks to Metallic Mimic—which you declare as a Human upon entry—each newly generated token hits the battlefield bearing its own +1/+1 counter. That fresh counter instantly arms the token with the exact Cauldron-granted exile ability you just used, allowing you to feed it right back into the cauldron to perpetuate an endless stream of creature enters-the-battlefield and leaves-the-battlefield triggers.