Thunderkin Awakener is a rare Creature — Elemental Shaman card from Core Set 2020 (M20), collector number 162. Current market price: $0.31 (foil $0.68), TCGplayer market prices via Scryfall.
Haste Whenever this creature attacks, choose target Elemental creature card in your graveyard with toughness less than this creature's toughness. Return that card to the battlefield tapped and attacking. Sacrifice it at the beginning of the next end step.