Cast the creature with morph or megamorph for its morph or megamorph cost by paying {0}, putting it on the battlefield face-down as a 2/2 creature.
Activate Primordial Mist by exiling the face-down creature face-up, allowing you to cast it from exile this turn.
Repeat.

Infinite creature ETB

Infinite creature LTB

Infinite storm count

Obscuring Aether

Primordial Mist

Ugin, the Ineffable

Activate Obscuring Aether by paying {1}{G}, turning it face-down as a 2/2 creature.
Activate Phyrexian Altar by sacrificing Obscuring Aether, adding {G}.
When Obscuring Aether dies, Yarus's second ability triggers, returning it from your graveyard to the battlefield face down, then turning it face up.
Deathmist Raptor triggers, returning it from your graveyard to the battlefield face down.
Activate Phyrexian Altar by sacrificing Deathmist Raptor, adding one mana of any color.
When Deathmist Raptor dies, Yarus's second ability triggers, returning it from your graveyard to the battlefield face down, then turning it face up.
Activate Phyrexian Altar by sacrificing Deathmist Raptor, adding one mana of any color.
Repeat.

Infinite colored mana

Infinite creature sacrifice triggers

Infinite death triggers

Yarus, Roar of the Old Gods

Deathmist Raptor

Phyrexian Altar

Cast the creature card with morph or megamorph from your hand for its morph cost by paying {0}.
Whenever the face-down creature enters the battlefield, Cloudstone Curio triggers, returning another creature with morph or megamorph to your hand from the battlefield.
Repeat.

Cloudstone Curio

Semblance Anvil

Activate Obscuring Aether by paying {1}{G}, turning it face-down as a 2/2 creature.
Activate Obscuring Aether by tapping it, adding {G}.
Activate Ashnod's Altar by sacrificing Obscuring Aether, adding {C}{C}.
When Obscuring Aether dies, Yarus' second ability triggers, returning it from your graveyard to the battlefield face-down, then turning it face-up.
Repeat.

Infinite colorless mana

Cryptolith Rite

Ashnod's Altar

Activate a basic land by tapping it, adding {1}.
Activate Obscuring Aether by paying {1}{G}, turning it face-down as a 2/2 creature.
Activate Earthcraft by tapping Obscuring Aether, untapping the basic land.
Activate Phyrexian Altar by sacrificing Obscuring Aether, adding {G}.
When Obscuring Aether dies, Yarus' second ability triggers, returning it from your graveyard to the battlefield face-down, then turning it face-up.
Repeat.

Combos with "Obscuring Aether"