Rukarumel, Biologist + Promised Kannushi + Ashnod's Altar + Energy Refractor

Rukarumel, Biologist

Promised Kannushi

Ashnod's Altar

Energy Refractor

How it works

1. Activate Ashnod's Altar by sacrificing Promised Kannushi, adding CC.
2. When Promised Kannushi dies, its soulshift ability triggers, returning itself from your graveyard to your hand.
3. Activate Energy Refractor by paying 2, adding .
4. Cast Promised Kannushi by paying .
5. Repeat.

Rukarumel, Biologist does the heavy lifting here by turning Promised Kannushi into a Sliver upon entering the battlefield, which allows it to leverage any synergies you might need, though its true home in this loop is the graveyard. By sacrificing Promised Kannushi to Ashnod's Altar, you generate two colorless mana, which triggers Promised Kannushi's Soulshift 7 ability to return itself right back to your hand. You then filter that colorless mana using Energy Refractor's mana-filtering ability, leaving you with just enough green mana to cast Promised Kannushi again and repeat the cycle indefinitely.