Briliant MTG card: Memnarch. Two abilities:
One selected opponent's card becomes an Artefact in addition to its other types. This effect does not end at the end of the turn.
Take control of one selected Artefact. This effect does not end at the end of the turn.
Neither requires tapping, so if you have enough mana you can theoretically take every monster they play. Memnarch is, as far as I can remember, a Wizard Legend, 5/6, costs something in the order of (5) to play and both of its abilities require blue mana.