Herigast, Erupting Nullkite | Cloudstone Curio | Molten Echoes

(and one other card)

Nonartifact, Nonlegendary Creature with a Generic Mana Cost

You have enough mana to cast the creature with a generic mana cost either for its mana cost, or for its emerge cost.
Molten Echoes naming any type that appears on the creature with a generic mana cost.

Cast the creature with a generic mana cost by paying its mana cost or emerge cost.
When the creature enters the battlefield,
Cloudstone Curio and
Molten Echoes trigger.
Resolve the
Cloudstone Curio trigger, choosing to return nothing to your hand.
Resolve the
Molten Echoes trigger, creating a token copy of the generic mana cost creature.
When the creature token enters the battlefield,
Cloudstone Curio triggers, returning the nontoken generic mana cost creature from the battlefield to your hand.
Cast the generic mana cost creature for its emerge cost by sacrificing the creature token created in step 5, and by paying ({0} magic symbol) as the token will have the same mana value.
Repeat from step 2.