Grim Poppet + Hulking Metamorph + Flourishing Defenses

Grim Poppet

Hulking Metamorph

Flourishing Defenses

How it works

1. Activate Grim Poppet by removing a -1/-1 counter from it, putting a -1/-1 counter on Hulking Metamorph.
2. Flourishing Defenses triggers, creating a creature token.
3. Activate Hulking Metamorph by removing a -1/-1 counter from it, putting a -1/-1 counter on Grim Poppet.
4. Flourishing Defenses triggers, creating a creature token.
5. Repeat.

This loop relies on an infinite dance of -1/-1 counters between Grim Poppet and Hulking Metamorph, which enters as a copy of Grim Poppet to share its counter-moving ability and ensure both creatures can target each other. Each time a counter is removed and placed onto the other, Flourishing Defenses watches the -1/-1 counter being put on a creature and triggers to create a 1/1 green Elf Warrior creature token. Because neither creature is destroyed by the counters during the process, you can repeat this back-and-forth activation indefinitely to generate an endless supply of creature tokens and enter-the-battlefield triggers.