Make Mists. Make More Mists. Make Mists Massive!
If you can't get mists, The Undying and Cursed Keeper can still take advantage of the spell kit. Late game you can use Atrocity on a high power Mistwraith or The Undying to finish off a nexus.
Wraithcallers are good choices for sacrifice/ephemeral targets such as Chronicler of Ruin and Splinter Soul. Mistwraiths and The Undying are other good targets if you are low on mana and are playing both the same turn. Cursed Keeper is the last choice but will work in a pinch, since it is not a good target for Scribe of Sorrow or Mist's Call.
Absorb soul can be used on creatures that would normally die, and to create targets for reviving early. The health can also help buy us time against aggro.
Possession can help take a high power unit from an enemy to remove blockers from fearsome attackers while using it to swing in. Also you can choose them as targets for spells such as Glimpse Beyond and Atrocity.
Kalista is not integral to the deck, but slots in nice at 3 mana for a 4/3 with fearsome. If you can get her to level up, ideally she will recall Mistwraiths as the game goes on since they will have a high power.
3.38
Shard Cost: 
17,900
40
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