Soul of Eternity is a rare Creature — Avatar card from The List (PLST), collector number CMR-50. Current market price: $0.27, TCGplayer market prices via Scryfall.
Soul of Eternity's power and toughness are each equal to your life total. Encore {7}{W}{W} ({7}{W}{W}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)