Agatha's Soul Cauldron + Lurking Roper + Kwain, Itinerant Meddler

Agatha's Soul Cauldron

Lurking Roper

Kwain, Itinerant Meddler

How it works

1. Activate Lurking Roper using Kwain's ability by tapping it, causing you to draw a card and gain 1 life, and allowing each opponent to do the same.
2. Lurking Roper triggers, untapping itself.
3. Repeat.

By using Agatha's Soul Cauldron to exile Kwain, Itinerant Meddler, you grant its tap ability to Lurking Roper, whose own reluctance to untap normally is completely bypassed by the synergy. Every time you activate the granted ability, Kwain's classic card-drawing and life-gaining effect triggers the Roper's passive untap condition right back. This creates an endless loop where you can repeatedly tap and untap the Roper, generating an astonishing bounty of card draw and lifegain for everyone involved.