I don't think there's a good way to deal with a T1 The Hollow other than trading very efficiently. Pinging with Selena's Mark + Canopy Barrage takes 4 mana and is way too slow. The good thing is that The Hollow generates random cards which may turn out to be useless to your opponent. Most of the time I just hope they don't get great cards and clear it once it's convenient to do so on T5 or so.