Havengul Lich + Grimgrin, Corpse-Born + Earthcraft + Shambling Ghast

Havengul Lich

Grimgrin, Corpse-Born

Earthcraft

Shambling Ghast

How it works

1. Activate a basic land by tapping it, adding one mana.
2. Activate Earthcraft by tapping Grimgrin, untapping a basic land.
3. Activate a basic land by tapping it, adding one mana.
4. Activate Earthcraft by tapping Shambling Ghast, untapping a basic land.
5. Activate Grimgrin by sacrificing Shambling Ghast, untapping Grimgrin and putting a +1/+1 counter on it.
6. When Shambling Ghast dies, it triggers, creating a Treasure token.
7. Activate the Treasure token by tapping and sacrificing it, adding one mana.
8. Activate Havengul Lich by paying 1, allowing you to cast Shambling Ghast from your graveyard this turn.
9. Cast Shambling Ghast from your graveyard by paying its casting cost.
10. Repeat.
11. Once you have infinite mana, you can repeat the loop but choose to give a creature -1/-1 in step 6 instead of creating Treasure, causing all creatures your opponents control to die.