Virulent Sliver is a common Creature — Sliver card from The List (PLST), collector number FUT-155. Current market price: $1.17, 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.)