Havengul Lich + Grimgrin, Corpse-Born + Shambling Ghast + A Realm Reborn

Havengul Lich

Grimgrin, Corpse-Born

Shambling Ghast

A Realm Reborn

How it works

1. Activate Grimgrin's ability from A Realm Reborn by tapping Grimgrin, adding one mana.
2. Activate Grimgrin by sacrificing Shambling Ghast, untapping Grimgrin and putting a +1/+1 counter on it.
3. When Shambling Ghast dies, it triggers, creating a Treasure token.
4. Activate the Treasure token by tapping and sacrificing it, adding one mana.
5. Activate Havengul Lich by paying 1, allowing you to cast Shambling Ghast from your graveyard this turn.
6. Cast Shambling Ghast from your graveyard by paying its casting cost.
7. Repeat.