You may skip the gameplay tutorial or introduction to the end for a very IMPORTANT note before you play it.

Introduction:

This is a deck that focuses purely on Dragon Soul, with additionally Witch's Cauldron adding more infinite value in it. It's not a powerful deck, but just wanted to show that you can do the dirty trick by exploiting Dragon Soul, you can get it infinite dragons or many shaman spells in your hand with just 5 cards combo. However, if you have very insane luck, you can do this on turn 5... but much harder than warlock's Darkest Hour.

And before we start, it is not an infinite combo as you can pull it off like 3 or 4 times to make it happen with very limited resources. You can still make them more with cheap shaman spells or other spells you have.

Gameplay:

Here is the combo forDragon Soul/Witch's Cauldron: Test Subject + Radiant Elemental (only 1!) + Embalming Ritual + Topsy Turvy or Forbidden Words.

The idea is very simple, but you need to get the Dragon Soul first, here is the step
of the combo:

1. play one Test Subject and one Radiant Elemental,
2. Cast Embalming Ritual on Test subject
3. then use Topsy Turvy or Forbidden Words on Test subject, then you can repeat it
again thanks to embalming ritual's mana cost discounted to 0.

That combo takes only 3 mana to go infinite cycle with EquippedDragon Soul or Placed Witch's Cauldron for infinite minions or many destruction shaman spells filled in your hand.

It is required 5 cards which needs the first combo I mentioned with additionally
Dragon Soul and Witch's Cauldron. Getting this combo is also easy if you want to get them before turn 10. I haven't playtested a lot for some reasons, but you can get it from tutor cards.

Here are some cards that tutor each of them:
Dead Ringer for Test Subject
[Hearthstone Card (Sand Binder) Not Found] for Radiant Elemental
Shadow Visions for Topsy Turvy or Embalming Ritual

The only one we are having trouble is getting the Dragon Soul (And some survivability), So how do we get it easily? Best solution is to draw cards and
there is one trick you can use:

Get the same Test Subject/Radiant Elemental combo as it is, except you add Power Word: ShieldThat way, you can draw many cards as possible. Just stop by when you have 8 cards in your hand.

If we lost our combo minions, Seance and Body Wrapper can return our combo tools back to us.

So that's all I got to say, this is not the best combo priest as there are much better alternative combo priests, it is just meant to showcase that you can exploit the game like Darkest Hour, this is wild of course, so it's not a gamebreaking.

Swapping Cards:

There are also some changes that can be applied to deck for different reasons:

2x Body Wrapper for 2x Arcane Giant for more big minions in mid game.
or
2x Grave Horror for 2x Seance for more refilling combo.
or
2x Body Wrapper for 2x Seance, just for more reliable combo refilling.

You can adjust those numbers of them according to what you need, or replace other AoE spells as well, but obviously do not change the core and tutor cards, unless you
got the plan.

Our Aoe spells are Circle of Healing and Embrace the Shadows for cheaper cost in clearing the board and activate Dragon's soul too. The reason why I keep Embrace the Shadows is that you can finish your opponent with Radiant Elemental + Witch's Brew for 32 damage, which is very unlikely, but I have done it anyways lol.

IMPORTANT NOTE:

I want to tell you before you play this deck, here is one BIG issue that is not related to winrate or such, it's a time consuming deck...

You have to play cards for less than 1 minute, after that, you will also have to wait another 1 minute from your opponent, due to cards animation playing for them, usually it takes like 3-4 seconds for each card you have played.

After waiting, your opponent will clear your minions, then you will use the combo again, and oh boy, the time is really CONSUMING.

This is like 2nd highest time consumption combo compared to old Shudderwock combo or priest Stonetusk Boar combo, except it's not a really big win condition... you can do this like more than 3 times to pull this combo, but you are wasting a ton of minutes for that. So this is why I don't play this deck much, it is not interesting to play after a few tries.

If you want to go for a meme though, you can go for it, you will not have fun anyways if you played it for the third time. The time consumption is real...

Anyways, if you feel this deck is weak, you can just use it as a blueprint to you.