Mulligans
General Mulligans
Quest: because Amara is pretty OP
Keleseth: because he's definitely OP
Northshire Cleric: because it is OP
Potion of Madness: also OP
Power word Shield: good to buff Northshire for a well-oiled card draw engine, and just for trading in general
Dark Cultist: great 3 drop, especially if you have another minion on the board.
Shellraiser: good for protecting Northshire, and is a great target for the Cultist buff to hit.
Vivid Nightmare can be used to help complete the quest much like twilight’s call, but you get the attack of the minion with the ability to heal it back up. It can also be used in cahoots with Umbra, like twilight’s call, to instantly trigger deathrattles. The main advantage to Vivid nightmare is its immense synergy with Carnivorous Cube, as it retains the destroyed minion, and summons 2 copies upon deathrattle activation.
Keleseth just happens to fit perfectly into the deck, and since the quest is minion based, it is fairly beneficial to have in your deck.
How to Win:
Aggro: You simply stall them until they run out of tempo. You use taunts such as Shellraiser and Belcher to soak up tons of damage while using potion of madness to put huge dents in their tempo and board state. Also in aggro matchups, they may ignore your Umbra if the trades required for them to kill it are too inconvenient, in which case you use umbra to go crazy with deathrattles.
Control: Getting the quest off is guaranteed to happen in long games, so you can use that to win fatigue games or just recover if you’re in a bad spot. Entomb and Lightbomb are key cards against control, as they can steal win conditions and clear the board respectively. Your win condition will most likely be either an unanswered N’Zoth, or an insane Umbra cube combo. Alternatively, you could just play Keleseth on turn 1 or 2 and slowly accumulate tons of value from having a “captured flag” effect in an online match.
Combo: This is where this deck will often struggle, you only have 1 line of defense against combo. That defense is Amara, many combo decks have a cap to their max damage, and most on average don’t reach that max damage by the time they need to pull of their combo. You just need to pressure them, have Amara, and hope that their combo: A) doesn’t involve Alextraza. B) Can’t deal 40 damage to you. However, seeing as combo decks usually run a lot of board clears, having a deathrattle themed deck can be useful in recovering from giant clears, potentially allowing you to kill them before they can begin to assemble their combo.