Mikaeus, the Unhallowed + Blue, Loyal Raptor + Yahenni, Undying Partisan

Mikaeus, the Unhallowed

Blue, Loyal Raptor

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing the other Dinosaur.
2. When the Dinosaur dies, its undying ability triggers, returning it from your graveyard to the battlefield without a +1/+1 counter on it due to the -1/-1 counter it will gain from Blue.
3. Resolve the Yahenni ability.
4. Repeat.

This loop turns Yahenni, Undying Partisan into an insatiable sacrifice outlet that feeds endlessly on a single dying Dinosaur, completely bypassing the normal limits of undying. The engine is glued together by Mikaeus, the Unhallowed, whose passive anthem grants the undying ability to your non-Human creatures in the first place. Meanwhile, Blue, Loyal Raptor alters how your Dinosaurs enter the battlefield by applying its own counters to them, ensuring that the necessary counter math resets the creature's state correctly with each iteration.