Mikaeus, the Unhallowed + Blue, Loyal Raptor + Ashnod's Altar

Mikaeus, the Unhallowed

Blue, Loyal Raptor

Ashnod's Altar

How it works

1. Activate Ashnod's Altar 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. Repeat.

This loop relies on the brilliant interaction between Mikaeus, the Unhallowed and Blue, Loyal Raptor to bypass the usual limitations of the undying mechanic. Normally, Mikaeus would grant undying that returns a creature with a +1/+1 counter, halting infinite loops—but because Blue, Loyal Raptor ensures your Dinosaurs enter with a counter of *each* kind on it (including the -1/-1 counter that somehow manages to cancel out the +1/+1 counter), the creature always returns with zero counters, keeping the cycle fresh. You can then feed this endless resurrection cycle directly into Ashnod's Altar to harvest infinite colorless mana alongside endless sacrifice and death triggers.