This is my update to a deck I saw on Jim Davis' stream soon after War of the Spark came out which he referred to as "Fishy Grixis".

His videos of it can be found here:
1 - https://www.youtube.com/watch?v=niNdDGj4OtQ
2 - https://www.youtube.com/watch?v=nJ1Xxsvu4s8

It seems it never took off in popularity, but I've always liked how it looked and Eldraine actually has a couple of new tools for it.

The core of the deck is made up of Soul Diviner, Kiora, Behemoth Beckoner, and Sarkhan the Masterless.

If you play Diviner on turn 2 and then Kiora on turn 3, you're able to use Diviner to eat a counter off Kiora and draw and then use Kiora's ability to untap Diviner so that you can do it again.
Then, on turn 4 you can tap a land for mana, use Kiora to untap it so you have five mana, play Sarkhan and make a 4/4 dragon, and then draw another card off Kiora's ability.
On turn 5 you can then begin attacking for 12 damage in the air every turn with Sarkhan's ability.

All of this means that the deck just has a lot of ways to draw cards as you simply go about your business of killing your opponent, and once you get set up you can easily end up drawing 3-5 cards every turn. It's lots of fun.

The new cards that Eldraine offers are Murderous Rider and Bonecrusher Giant, and I think they both exist as clear improvements to the deck.

Murderous Rider serves to replace Bedevil, which reduces the deck's need for red mana and gives you an extra threat that's also an actual source of life-gain. Grixis can struggle to gain life in its colours, and having a way to start gaining life after you put your opponent into topdeck mode can be very helpful.

Bonecrusher Giant is absolutely terrific in this deck because it allows you to cut more piddly removal spells like Disfigure and Carnival // Carnage while adding yet another threat to the deck that also draws a card off Kiora when you play it.
Going turn 3 Kiora, turn 4 tap and untap a land to add 5 mana, Stomp a creature + play Bonecrusher Giant and draw a card just feels great.

The other major change I've made is putting Sphinx of Foresight in the 4-drop slot. This is to replace Nicol Bolas, the Ravager // Nicol Bolas, the Arisen which was lost with rotation, and I think it fits quite well.

In a deck that wants to hit its land drops and find its tools of trade, the scry 3 on your first upkeep can sometimes singlehandedly decide whether you win or lose - I've kept a two land hand and then scryed 3 non-land draws straight to the bottom a couple times now already.

As well, a 4/4 flyer for 4 is on-rate, a 4/4 flyer that draws a card on ETB (thanks to Kiora) is above-rate, and that scry 1 every upkeep is more than just flavour text. Unlike Nicol Bolas, the Ravager // Nicol Bolas, the Arisen the Sphinx isn't legendary, so once you get a couple of these in play they basically guarantee that everything you draw is useful to you. You really notice the difference in a topdeck war when one of you is scrying 1 every turn and one of you isn't.

Other than that, I've upped the number of Ritual of Soots to 3 in order to kill mana dorks and hydras out of the green decks, and I've changed the number of planeswalkers at the top-end to 4 Sarkhan the Masterless and only 2 Nicol Bolas, Dragon-God

Having so many more creature threats now, the deck feels like it revolves much more around winning with Sarkhan than it does with Bolas. Nicol Bolas can copy Sarkhan's ability to make a dragon and can otherwise slowly drain your opponent out of resources with his +1, but he just doesn't feel to me like he does enough on his own to warrant 4 whole copies like Jim Davis had him at.

Finally, to briefly mention the sideboard: This is tuned primarily to beat Oko decks, but hopefully Oko, Thief of Crowns will be getting banned in the near future and I can change it to one that's more normal. :)