Leyline of Lightning is a rare Enchantment card from Guildpact (GPT), collector number 68. Current market price: $0.25 (foil $3.00), TCGplayer market prices via Scryfall.
If this card is in your opening hand, you may begin the game with it on the battlefield. Whenever you cast a spell, you may pay {1}. If you do, this enchantment deals 1 damage to target player or planeswalker.