Throom, Lyev Stalwart

Knights you control get +1/+1 and lifelink.
Whenever a Knight enters the battlefield
under your control, you may pay {1}{w}{w}. If you
do, exile target nonland permanent for as long as
Throom, Lyev Stalwart is on the battlefield.
Whenever a Knight enters the battlefield
under your control, you may pay {1}{u}{u}. If you
do, permanents you control have hexproof until
end of turn.