Hearthpwn

I've waited 2 years for the APM Giant Priest to be good. Now w Thrive, Cleric, Devout - half of the deck are basically tutors. The combo is simple: Radiant, Test, Shield, Embalming, Topsy/Smite. Draw your deck, drop the giants. You need to learn and practice it a lot to actually win games. 1 missclick, 1 misorder, 1 wasted sec on the combo turn and it's over.
I've tested a lot of variations this month and comfortably ended up on this one.

Mulligan: Keep Radiant/Sandbinder, Test/Ringer, never keep any spells unless you have the above (because you have much more tutors for them unlike the minions), can keep Smite vs aggro.

Details:
You don't even need shield. No draw, but with few giants it works.
You don't even need the Radiant. With just Topsy, Embalming, Test you need to calc how many spells are played. Fe: at 5 mana you can play 4 Embalm, 6 Topsy, if 10 is too much you can jam Shield in for +1 Shield = -1 Topsy.
Try to play Devout first, because it's random. Prefer Shield/Embalming from Discover because either Smite or Topsy works.
Embalming is a better choice then Shield with bunch of Giants in hand.
Smite works, you need to Embalming, Smite first to put the next shielded Subjects at 3 hp. When the hand starts getting full just use the remaining stuff on the board, Embalm on Pupil is annoying.
Vs Aggro is hard, manage your turns to maximize survival w building the combo.
Vs Control/Combo you usually draw into Illucia to setup lethal unless you have the combo early.