Leshrac's Sigil is a uncommon Enchantment card from Ice Age (ICE), collector number 144. Current market price: $0.31, TCGplayer market prices via Scryfall.
Whenever an opponent casts a green spell, you may pay {B}{B}. If you do, look at that player's hand and choose a card from it. The player discards that card. {B}{B}: Return this enchantment to its owner's hand.