I had this idea for the deck since Da Undatakah was first announced.
What's the goal of the deck, you may ask? Ah, yes, let me show you the simple idea:
You first try to get Primalfin Champion dead as soon as possible, if you manage to buff it then you are good to go, you get some more free value for your mighty Loa (cuz MY LOA IS GONNA TRASH YA). Then, you try to get Immortal Prelate and Sergeant Sally dead, buffing them is even better than buffing the murloc, since they get huge value from those.
Then you just have to dif through your whole deck to get Da Undatakah. You play him, he gets those 3 deathrattles. How does this work? Well, now you can freely buff him- every spell that you cast on him will go back to your hand because of Primalfin Champion. When he dies, he deals his damage to the whole enemy board (hooray Sergeant Sally), which is 8 damage minimum, so it is a HUGE clear. But wait, there's more! The shuffled Da Undatakah keeps all his buffs and deathrattles! When you draw it and play it for the second time, those deathrattles DOUBLE! Yes, they simply DOUBLE UP! It means that you keep getting bigger and bigger Da Undatakah, which possibly has things like Taunt from Spikeridged Steed and also gains the 2/6 Deathrattle on top of it!
This deck has crazy value potential, but there is one huge IF:
If your opponent runs silence, you are screwed.
Which is exactly why we run exactly one Getaway Kodo in the deck! We also have some other baits for silences, including Lynessa Sunsorrow or our core combo cards (Primalfin Champion, Immortal Prelate, Sergeant Sally). The deck has HUGE potential, but it needs to be able to stay alive for long enough and dodge the silences.
It is a fun deck and I don't predict it being even tier 3 or 4 once the meta settles down, but the fun can be great during first 2-3 weeks of the expansion.
Good luck and may the luck, and the fun, be with you! :)