Imposter :
Super fun to build around.
The general idea here with this deck is, having options.
Your avatar choice will be dictated by how the game is going.
Early on turn 3 paying 3 mana to shift into pathfinder so you can on your 4th turn do pathfinder things for a hopeful turn or two.
Avatar of air is going to help you get in range and out of danger. As well as the option to push your minions into the right spot at the right time.
Deathspeaker is an option if you have a genesis minion in the cemetary. There are some good choices in this deck and dont forget to keep an eye on your opponents cemetary for use as well.
Archimago this is where you can really turn the tide and ideally you already have 3 magic spells in the cemtary ready to go. Or very late game you may have 6 magics ready to go.
The deck is built with archi in mind and alot of the damage is gonna be through those cheap magic spells
Being able to hit for 6 damage on 4 mana with double.firebolts, magic missles or lightning bolt feels pretty good.
Flamecaller is here mostly for a deathblow option as a last resort. Or if the game went your way luckily with having dead fire minions sure you could use them to push some serious damage. But not every minion in the deck has flamecaller in mind and that is okay flamecaller is not the primary secondary or 3rd option here. Just a solid backup plan that doesnt really hurt to have in the collection
I would consider this a burn style deck