Halo-Charged Skaab is a common Creature — Zombie card from March of the Machine (MOM), collector number 60. Current market price: $0.16 (foil $0.26), TCGplayer market prices via Scryfall.
When this creature enters, each player mills two cards. Then you may put an instant, sorcery, or battle card from your graveyard on top of your library. (To mill two cards, a player puts the top two cards of their library into their graveyard.)