Ratadrabik of Urborg + Sarkhan, the Dragonspeaker + Ashnod's Altar

Ratadrabik of Urborg

Sarkhan, the Dragonspeaker

Ashnod's Altar

How it works

1. Activate Sarkhan's first loyalty ability by putting a loyalty counter on it, causing it to become a legendary 4/4 Dragon creature with flying, indestructible and haste.
2. Activate Ashnod's Altar by sacrificing Sarkhan.
3. When Sarkhan dies, Ratadrabik triggers, creating a token copy of Sarkhan that isn't legendary.
4. Repeat using the Sarkhan token.

By animating Sarkhan, the Dragonspeaker with its own loyalty ability, it temporarily transforms into a legendary creature that can be sacrificed safely to Ashnod's Altar for colorless mana. This death triggers Ratadrabik of Urborg, which creates a nonlegendary token copy of Sarkhan that retains the planeswalker's activated abilities while also being a Zombie thanks to Ratadrabik's static type-altering effect. Because that token is not legendary, repeating the loop with subsequent tokens bypasses the legendary rule entirely, fueling an endless cycle of sacrifices, death triggers, and infinite colorless mana.