(I just started a new free account) & This deck has taken me all the way from 25 to 10. Would love to know how it does in the higher ranks. Going to continue playing with it to see how high I could take it, but I thought I would share for those of you who don't have the other two needed legendaries in this deck (Zilliax and Zuljin) + Masked Contenders.
Mulligan for Secretkeeper, Secrets (Especially if you have Sunreaver Spy which you need to keep if you have a secret to play) , Eaglehorn Bow (Also obviously great to keep with secrets), Explosive Trap against aggro such as Shaman, or Druid. Mulligan secrets based on what class you're playing against... Explosive Trap for Aggro, Freezing Trap for Giants, etc. Always keep Subject 9.
Go face mostly, unless there is an unavoidably large minion on the opponents board. You have a lot of great removal spells for that though.
Always use Kill Command with a beast for 5 damage instead of 3, unless in dire need of removal.
Lifedrinker, Kill Command, Baited Arrow are all great finishers.
Gladiator's Longbow has won me quite a few games.. 5 damage no cons is great!

Enjoy xx