Out of all the Old Gods it actually might be N'Zoth, the Corruptor that ends up being the most relevant of them all. C'Thun needs an entire deck built around it and Yogg-Saron, Hope's End has a bit too much RNG to be played in a wide variety of decks. Y'Shaarj, Rage Unbound on the other hand is largely rejected as a competitive card whatsoever, at least in the current meta. So if you've got N'Zoth in your collection here are some decks that should give you a chance to it to good use!
Control Rogue may not be a popular archetype, but more than ever it is competitive and an entirely viable deck to play. N'Zoth has really helped it, giving it an out against other control decks when it gets to the late game. Shadowcaster is unique to Rogue and also a very good card in this situation. Revive three Sylvanas Windrunner and see if they can deal with that!
The initial idea was to build a deck around N'Zoth, but as I was playing the deck i realized that there were just a few cards that were repeating and I was lacking healing. So I decided to remove most repeated card and add Reno. I have fun playing this deck, it got me rank 10 last season and rank 5 in another season, but I see it has some weakness, like against some aggressive decks such zoo lock.
Chillmaw has also found itself a nice home alongside N'Zoth. You'll frequently find it alongside other late game dragons including Deathwing, Dragonlord if they're greedy like this Paladin deck is.
A very greedy control paladin deck that can have a good early game and incorporates dragons and N'Zoth! i found this deck extremely successful even against the aggro matchup. It can keep tempo in the early game against a well constructed zoo deck and then completely destroy them when reaching the mid-late game. this deck also constantly gains card advantage due to the fact it uses N'Zoth which interacts with near enough every minion in this deck.
This Deathrattle Rogue is probably the most refined of all these guides. It seems most optimized, the least greedy, and ready to win some games on the ladder. Give it a shot if you've got the tools!
MVPs of the deck:
Shadowcaster: Very strong and very versatile. Though it often times ends up being a 6 drop instead of a 5 drop. Copy a VanCleef for a second chance at a crazy stat'd minion (much easier to combo at 1 mana!). Copy a defender of argus for insane value. Copy an azure drake for more cycle. If you can manage it, Copy N'Zoth himself!
That's it for this roundup, but if you find any deck guides you think are worth highlighting, make sure to send them our way!