Descent into Avernus is a rare Enchantment card from Secret Lair Drop (SLD), collector number 2176. Current market price: $17.64, TCGplayer market prices via Scryfall.
At the beginning of your upkeep, put two descent counters on this enchantment. Then each player creates X Treasure tokens and this enchantment deals X damage to each player, where X is the number of descent counters on this enchantment.