Averna, the Chaos Bloom is a rare Legendary Creature — Elemental Shaman card from Commander Legends (CMR), collector number 269. Current market price: $0.33 (foil $0.51), TCGplayer market prices via Scryfall.
As you cascade, you may put a land card from among the exiled cards onto the battlefield tapped. (Do this after the last card is exiled but before deciding whether to cast a nonland card.)