Contested War Zone is a rare Land card from Mirrodin Besieged (MBS), collector number 144. Current market price: $0.33 (foil $0.88), TCGplayer market prices via Scryfall.
Whenever a creature deals combat damage to you, that creature's controller gains control of this land. {T}: Add {C}. {1}, {T}: Attacking creatures get +1/+0 until end of turn.