Sidewinder Sliver is a common Creature — Sliver card from Time Spiral Remastered (TSR), collector number 43. Current market price: $0.26 (foil $1.02), TCGplayer market prices via Scryfall.
All Sliver creatures have flanking. (Whenever a creature without flanking blocks a Sliver, the blocking creature gets -1/-1 until end of turn.)