Mind Drill Assailant is a common Creature — Rat Warlock card from Bloomburrow (BLB), collector number 225. Current market price: $0.11 (foil $0.27), TCGplayer market prices via Scryfall.
Threshold — As long as there are seven or more cards in your graveyard, this creature gets +3/+0. {2}{U/B}: Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)