Giant-Killer Tripwire

Flash
Giant-Killer Tripwire enters the battlefield tapped.
At the beginning of your end step, you man tap Giant-Killer Tripwire.
{ut}: Tap target creature attacking you. It loses hexproof and indestructible and has toughness 1 until end of turn.
Giant-Killer Tripwire has hexproof as long as you control three or more Plains.