Hearthpwn

Only use I have for him is in my Priest Silence deck.  He can combo well with the 0-cost Silence for a turn 5 8/8.  First time I ever saw it was in arena where it cost my opponent many, many cards where I quickly learned Reaver should NEVER be in play without silence on him, unless you can somehow invent a strategy that involves burning cards.

Things like Wailing Soul work real well (though expensive) if you're packing an Ancient Watcher too.

It would be all theory and no practice.  I have faith in you being able to figure out which cards to replace.

This card is good for a silence deck--Priest, namely, since you can drop 0 cost silences for a turn 2 4/5.  Ancient Watcher works if your deck has -too many silences- because that surplus turns into one beefy early game card.

When Stalagg or Feugen are dropped, being silenced doesn't affect the first one, so to cancel Thaddius you would need to morph the first so that "Stalagg" or "Feugen" doesn't end up in the discard pile, fulfilling Thaddius's prerequisites.

I managed to get the second guy out with a Shaman then use Reincarnation to kill Stalagg, giving me an 11/11 Thaddius as well as a 7/4 Stalagg who summons a SECOND Thaddius when he dies. This worked well since the opponent didn't have the chance to silence Stalagg since it reincarnated the turn he was played.