Mulligans
General Mulligans
If you're playing this deck, you really only want to play it like any other thief rogue deck unless you don't think you can win that way.
Aggro Mulligans
You aren't going to win this matchup, most likely.
Control Mulligans
Get combo pieces. Plan for Plan 1 if it's a low armor control deck, Plan for Plan 2 if it's a druid or control warrior.
Plan 1- Step 1: Equip Necrium Blade. Step 2: Get Necrium blade to 1 durability. Step 3: Play Hakkar, break weapon. Step 4: Play Hemet. Step 5: Play Academic Espionage and spiders, Lab Recruiting them. Step 6: ??? Step 7: Tess, wait out your opponent with value until they kill themselves with Corrupted Blood.
Plan 2- Step 1: Equip Necrium Blade. Step 2: Get Necrium Blade to 1 durability. Step 3: Play Kobold Illusionist with just Hakkar in hand. Step 5: Break the weapon. Step 6: Prep. Step 7: Necrium Vial on the 1/1 Hakkar. Step 8: Hemet. Step 9: Academic Espionage, fill deck up with value. Step 10: ??? Step 11: Tess, wait out your opponent with value until they kill themselves with Corrupted Blood.
Use Gral to get big stats and use any extra deathrattle activation on him to get more value.