Virulent Sliver is a common Creature — Sliver card from Future Sight (FUT), collector number 155. Current market price: $0.54 (foil $7.59), TCGplayer market prices via Scryfall.
All Sliver creatures have poisonous 1. (Whenever a Sliver deals combat damage to a player, that player gets a poison counter. A player with ten or more poison counters loses the game.)