Hofri Ghostforge + Mistmoon Griffin + Phyrexian Altar

Hofri Ghostforge

Mistmoon Griffin

Phyrexian Altar

How it works

1. Activate Phyrexian Altar by sacrificing Mistmoon Griffin, adding one mana of any color.
2. Mistmoon Griffin dies, triggering itself and Hofri Ghostforge.
3. Resolve the Hofri Ghostforge trigger, exiling Mistmoon Griffin from your graveyard and creating a token copy of Mistmoon Griffin that has "When this creature leaves the battlefield, return the exiled card to your graveyard".
4. Resolve the Mistmoon Griffin trigger, returning nothing from your graveyard to the battlefield.
5. Activate Phyrexian Altar by sacrificing the Mistmoon Griffin token, adding one mana of any color.
6. The Mistmoon Griffin token dies, triggering itself twice.
7. Resolve the Mistmoon Griffin token's trigger granted by Hofri Ghostforge, returning Mistmoon Griffin from exile to your graveyard.
8. Resolve the other Mistmoon Griffin trigger, returning Mistmoon Griffin from your graveyard to the battlefield.
9. Repeat.