Nim Deathmantle | Ashnod's Altar | Ashaya, Soul of the Wild

(and one other card)

Activate
Ashnod's Altar by sacrificing
Ashaya, adding ({C} magic symbol) ({C} magic symbol) .
When
Ashaya dies,
Nim Deathmantle and Omanth's second ability trigger.
Resolve the
Omnath trigger, dealing 3 damage to any target.
Resolve the
Nim Deathmantle trigger, causing you to pay ({4} magic symbol) to return
Ashaya from your graveyard to the battlefield, and attaching
Nim Deathmantle to it.
When
Ashaya enters the battlefield,
Omnath's first and second abilities trigger.
Resolve the first
Omnath trigger, creating a 5/5 Elemental creature token.
Resolve the second
Omnath trigger, dealing 3 damage to any target.
Activate
Ashnod's Altar by sacrificing the Elemental token, adding ({C} magic symbol) ({C} magic symbol) .
When the Elemental dies, Omanth's second ability triggers, dealing 3 damage to any target.
Repeat.
If you control a nontoken creature that has haste, you may instead sacrifice it, and then tap it each iteration to get infinite green mana and colorless mana.