Ornstein and Smough

First strike, Trample, Ornstein and Smough cannot be sacrificed.
If Ornstein and Smough would be dealt damage, instead prevent that damage and put a -1/-1 counter on them. When Ornstein and Smough dies, and opponent chooses Dragonslayer Ornstein or Executioner Smough, search your library for a card with the same name and put it onto the battlefield with a +1/+1 counter.