Mulligans
General Mulligans
Call to Arms is a great card in almost every situation. The rest of your deck is very versatile in mulligans, but ideally you will be able to curve out a 1-drop or secret into one of your many 2-drops.
Avenge is a very strong card, giving a minion +3/+2 stats for 1 mana, creating minions that are hard for your opponent to deal with early on.
Aggro Mulligans
Noble Sacrifice is a great card to gain tempo against aggro decks and preserve your board.
Sacred Trial is a massively overlooked card, as it can often find large amounts of value in board-focused decks as most players do not play around it.
Both Muster for Battle and Haunted Creeper can provide you with an early board to contest your opponents until you can reach your turn 6, 7, and 8 plays.
Avenge can give you a massive and sudden advantage against other aggro decks, often able to turn around or generate a massive early lead.
Midrange Mulligans
Against decks that play bigger minions, Sacred Trial can catch many opponents off guard, and kill off huge minions for 1 mana.
This deck plays very well against midrange, as you often will out-value your opponent with cards such as Call to Arms, Dr. Boom, Tirion Fordring, and 5 secrets from Mysterious Challenger.