Averna, the Chaos Bloom is a rare Legendary Creature — Elemental Shaman card from Foundations Jumpstart (J25), collector number 80. Current market price: $0.36, 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.)