Activate Xenagos's first ability by putting a loyalty counter on it, adding at least {3}{R}{R}{G}{G}.
Cast Domri by paying {1}{R}{G}.
Domri enters the battlefield, triggering Cloudstone Curio, returning Xenagos from the battlefield to your hand.
Activate Domri's first ability by putting a loyalty counter on it, adding {R/G}.
Cast Xenagos by paying {2}{R}{G}.
Xenagos enters the battlefield, triggering Cloudstone Curio, returning Domri from the battlefield to your hand.
Repeat.
Once you have infinite mana, you may instead activate Xenagos' second ability to get infinite creature tokens.

Infinite creature tokens

Infinite creature ETB

Infinite green mana

Infinite red mana

Cloudstone Curio

Xenagos, the Reveler

Domri, Anarch of Bolas

Activate Domri's first ability by putting a loyalty counter on it, adding {R/G}.
Cast Wrenn and Six by paying {0}.
Wrenn and Six enters the battlefield, triggering Cloudstone Curio, returning Domri from the battlefield to your hand.
Activate Wrenn and Six's second ability by removing a loyalty counter from it, dealing 1 damage to any target.
Cast Domri by paying {1}.
Domri enters the battlefield, triggering Cloudstone Curio, returning Wrenn and Six from the battlefield to your hand.
Repeat.

Infinite damage

Bard Class

Wrenn and Six

Activate Lithatog by sacrificing Sword of the Meek.
Skittering Precursor triggers, creating a 0/1 Eldrazi Spawn creature token.
When the Eldrazi Spawn enters the battlefield as a 1/1 due to Domri, Sword of the Meek triggers, returning Sword of the Meek from your graveyard to the battlefield attached to the Eldrazi Spawn.
Resolve the Lithatog ability, giving it +1/+1 until end of turn.
Repeat.

Combos with "Domri, Anarch of Bolas"