Activate Grim Poppet by removing a -1/-1 counter from it, putting a -1/-1 counter on Mirrorhall Mimic
Flourishing Defenses triggers, creating a creature token.
Activate Mirrorhall Mimic by removing a -1/-1 counter from it, putting a -1/-1 counter on Grim Poppet.
Flourishing Defenses triggers, creating a creature token.
Repeat.
This clever loop turns the back-and-forth movement of -1/-1 counters into an endless supply of bodies, fueled entirely by the static enchantment Flourishing Defenses. By having Grim Poppet and Mirrorhall Mimic target each other back and forth with their respective counter-removal abilities, you continuously trigger Flourishing Defenses to flood the board with Elf Warrior tokens. Because both creatures naturally enter with or accumulate counters to spend, you can bounce the counters indefinitely between them without running out of fuel.