The Bloodbile Swarm is a rare Legendary Creature — Elemental Insect card from Alchemy: Reality Fracture (YFRA), collector number 19.
Ward—Sacrifice a Blood artifact. Other creatures are Blood artifacts in addition to their other types and have "{1}, {T}, Discard a card, Sacrifice this creature: Draw a card." Whenever a player sacrifices a nontoken creature or discards a creature card, exile it. It perpetually gains prismatic. You may cast it until the end of your next turn.