Hearthpwn

if you don't draw undertaker and its supporting minions in 1-4 turn, ur dead

Thoughts on replacing the 2x Knife Juggler with 2x Amani Berserker?

Knife jugglers combo really well with mirror images, and is a scarier turn 2 play. I wouldnt replace it with berserkers in a fast-paced mage deck like this. Berserkers are better suited in a more midrange deck where you can afford to take your time to ping it with heropower the turn after its played.

Totally understandable, I forgot to mention I was running a less aggressive variation of this deck with 2x Sludge Belcher instead of 2x Mirror Image though I have since switched to this build. I'm now debating trading out 2x Sorcerer's Apprentice for 2x Amani Berserker. I don't often benefit from the spell cost deduction tbh, the berserker is stickier to the board with 3hp and typically draws out a removal spell or some sort of awkward trade.

Are there any good cards to fill the slot if I'm missing Thalnos?

Classical Kobold the Cheap Thalnos

Currently I've been using another secret, a duplicate, instead. I've hit rank 1 last night, and duplicate + Leper Gnome or Knife Juggler is just too good. Kobold is kind of a dumb option because you don't /need/ the spellpower, it's just a third loot hoarder to trigger undertaker.

I dropped in another cheap death rattle to add value to the undertaker. The Thalnos is great because of the death rattle and the card draw.

I put in Haunted Creeper. It's got good synergy with both Undertaker and Knife Juggler.