Agatha's Soul Cauldron + Spike Feeder + Scion of the Swarm

Agatha's Soul Cauldron

Spike Feeder

Scion of the Swarm

How it works

1. Activate Scion of the Swarm using Spike Feeder's second ability by removing a +1/+1 counter from it, causing you to gain 2 life.
2. Scion of the Swarm triggers, putting a +1/+1 counter on it.
3. Repeat.

This clever loop turns simple counter-manipulation into boundless life by bridging a few disparate abilities. With Agatha's Soul Cauldron exiling Spike Feeder, its activated abilities—specifically the one that trades a +1/+1 counter for 2 life—are granted to Scion of the Swarm, provided Scion has a +1/+1 counter on it. You can then use that acquired ability to strip a counter from Scion of the Swarm for a burst of life, which immediately triggers Scion's own static ability to put a +1/+1 counter right back on itself. This creates a self-sustaining cycle of lifegain and counter replacement that can be repeated as many times as you desire.