CardName: Death of Knowledge
Cost: bb
Type: Enchantment
Pow/Tgh: /
Rules Text: Whenever an opponent discards a card, you may return target
creature with converted mana cost less than the number of
cards in that player's graveyard from that player's
graveyard to the battlefield.
Flavour Text:
Set/Rarity: Link's Unplaced Cards Rare
Death of Knowledge
R
Enchantment
Whenever an opponent discards a card, you may return target creature with converted mana cost less than the number of cards in that player's graveyard from that player's graveyard to the battlefield.
I gave this such a low mana cost because it is so conditional.