Leyline Immersion is a rare Enchantment — Aura card from March of the Machine: The Aftermath (MAT), collector number 161. Current market price: $1.27 (foil $1.51), TCGplayer market prices via Scryfall.
Enchant legendary creature Enchanted creature has ward {2} and "{T}: Add five mana in any combination of colors. Spend this mana only to cast spells."