Stage 1
Boss: Grace, 123 HP
Recommended Cards:
Various walls.
Blessing: Sanctuary
Strategy
There are two main approaches to this stage. Both require the use of Blessing: Sanctuary. The first and easiest way involves summoning two creatures next to each other and placing Sanctuary on both of them. Grace will then repeatedly cast Double Stab and Whirlwind Strike onto those two creatures and thus kill herself off.
Obviously as you need to use Sanctuary, you will need at least one priest to finish this stage, however the rest of the slots can be filled up with any other class although more priests will increase the chances of drawing the skill, and you will need at least two priests for stage two anyway.
Mausoleum 1
It's worthwhile to note that any other creatures summoned and kept on the board will be killed instantly and will also waste spells that could've been reflected back onto Grace. A popular tactic is to place down cards and dig them up immediately. This get's rid of unneeded cards and is especially effective with Unicorn, Unicorn Mirager and Unicorn Tempest
The second approach is similar to the one players use to defeat Akanthia in stage two. This involves using a Sylvi Bladesoul or Sylvi Protege with Sanctuary. The Sylvi will reflect back spells while moving up to Grace. A warrior can cast Encourage and Command: Heroic and the Sylvi will take down the rest of Grace's heath.
Of course, it is probably possible to force the boss down simply by throwing creatures at her, but this will likely take a long time and be made extremely difficult by her unique hero creatures. For this, you will need a mage to remove her {{c|Chained Soul]] from the units that possess it.
Stage 2
Boss: Queen of the Damned, Akanthia, 500 HP
Recommended Cards:
Sensei Callista
Sylvi Bladesoul
Command: Heroic
Blessing: Sanctuary
Swift Raid
Strategy
Like the second approach with stage one, it involves the use of Blessing: Sanctuary and a creature that attacks 3 or more times per turn. Attempting this with any creature with less health than an Epic Sylvi Bladesoul will likely fail, because Akanthia uses spells and Princess Sarya which do not deal damage, but can kill your creature nonetheless. The absolute minimum class configuration that can attempt this stage is with two priests and one warrior. The fourth slot is usually played by a mage but any class can play in that slot, although rangers will not be able to do anything (note that Swift Raid can massively improve damage potential before the wipe). At the start the master starts off with godlike archers that will deal heavy damage to Akanthia. At that point it is ill advised to put anything down other than extra archers, as in a few turns Akanthia will wipe the whole map clean. Akanthia can summon before the map wipe if she is provided with space, so using a high tier damage rune can cause her to kill her own unit. After that, she will summon several rows of bats. The players end their turns until any of them have a Sylvi Bladesoul, the priests have at least one Sanctuary and the warrior has buffs. At that point the Sylvi is played and the priests take in turns placing shielding it with Sanctuary while the warrior keeps buffing it. The burrow ability of the Sylvi and the flying ability of Akanthia's bats will ensure that the Sylvi reaches Akanthia within 2 turns. Akanthia will periodically cast an AoE spell version of Sarya's withering aura onto the Sylvi that stacks with itself. Alongside Sarya herself, this will reduce the Sylvi to 1 hp given it is an epic Sylvi Bladesoul, and will further kill the Sylvi if Akanthia casts the AoE spell again. Priests can use dispel to remove Akanthia's spell, and Sarya can be disabled or removed to stop the withering aura ability. The 4th player, given a mage uses spells such as Weaken, Frost Nova, Petrify, Charm or Deep Freeze to prevent enemy creatures dealing damage to the other players while the Sylvi works on killing Akanthia. Given a different class other than mage, other players can use Nimble elves such as Elven Blessed Samurai and Elven Rebel to prevent damage. Non-nimble creatures should not be played due to Akanthia's spells that destroy and then absorb the life of those creatures, although like in stage one it is beneficial to play unicorn cards and then immediately dig them up again.
Another way is to get one of your allies below half health, then having that ally summon Savior Carella and buff it with Blessing: Sanctuary.
Source:http://rise-of-mythos.wikia.com/wiki/King%27s_Mausoleum