Lockdown Operative

When Lockdown Operative attacks, mill two.
Then for each card milled this way, you may look
at defending player's hand and exile a card from
their hand or target nonland permanent they
control on the battlefield that shares a type as the milled card.
At the beginning of your upkeep or if Lockdown Operative leaves the battlefield, return all cards
exiled by it to their owners' hand.