Bellowing Aegisaur + Scurry Oak + Pandemonium

Bellowing Aegisaur

Scurry Oak

Pandemonium

How it works

1. Give Bellowing Aegisaur indestructible by any method.
2. Deal damage to Bellowing Aegisaur.
3. Bellowing Aegisaur triggers, putting a +1/+1 counter on each other creature you control.
4. Scurry Oak triggers, creating a 1/1 Squirrel creature token.
5. The Squirrel enters the battlefield, triggering Pandemonium, dealing 1 damage to Bellowing Aegisaur.
6. Repeat from step 3.

This loop transforms a single instance of damage into an unstoppable engine by turning creature tokens into a self-sustaining trigger. Scurry Oak acts as the heart of the machine, generating a 1/1 green Squirrel creature token every time counters are added to it, which in turn triggers Pandemonium to deal damage. That damage strikes Bellowing Aegisaur, whose enrage ability uses the initial investment of indestructible protection to bounce the energy back out, placing a +1/+1 counter on all your other creatures while simultaneously fueling Scurry Oak's evolve and counter-triggered abilities to keep the sequence spinning endlessly.