Hoarder's Overflow is a uncommon Enchantment card from Bloomburrow (BLB), collector number 141. Current market price: $0.21 (foil $0.36), TCGplayer market prices via Scryfall.
When this enchantment enters and whenever you expend 4, put a stash counter on it. (You expend 4 as you spend your fourth total mana to cast spells during a turn.) {1}{R}, Sacrifice this enchantment: Discard your hand, then draw cards equal to the number of stash counters on this enchantment.