Mulligans
General Mulligans
Surviving the first phase is fairly easy. Just have enough board clears and you'll be fine. Try to mill him once you have the chance, but don't invest too much into it.
Keep the Harvester of Envy for the 2nd phase, as it's going to practically win you the match. Mindreader Illucia is a good alternative if the board is filled and you want to just deal like 90dmg in one turn with his OP spell.
In his 2nd phase, try to steal his OP spell that OTKs you if there are 4-5 minions on the board (with the Harvester of Envy). Other than that, it should be smooth sailing. You may want to mill him in his first stage, but that’s not needed for the win.
Try to play Mi’da early on, so you can benefit from her OP lifesteal effects (combine with Grave Rune).
You don’t have to complete the Tavern Brawl in one go, but it’s still pretty easy to do so with this deck. You can also restart the match from the menu if you want to have a better starting hand.
Good luck, and have fun!