Terisian Mindbreaker is a rare Artifact Creature — Juggernaut card from The Brothers' War Promos (PBRO), collector number 83p. Current market price: $3.70 (foil $4.49), TCGplayer market prices via Scryfall.
Whenever this creature attacks, defending player mills half their library, rounded up. Unearth {1}{U}{U}{U} ({1}{U}{U}{U}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)