Nahiri, the Harbinger was a Modern sensation two years ago, reinvigorating Jeskai Control with a versatile planeswalker that could fix your draws, remove a wide range of threats, and end the game by tutoring for Emrakul, the Aeons Torn if left unchecked. But just as quickly as it ascended, it was gone, relegated to the fringes of the format and often appearing as a singleton, if at all, in various decks but not much more.
I never really got why Nahiri fell out of favor so quickly, so today I'm revisiting it with an update on a deck Todd Stevens built a while ago and dubbed Sun and Moon. It's really a W/R Control deck with some prison components like Blood Moon and Chalice of the Void, though the latter has been removed from this list since it's not well-positioned currently.
Without blue, the deck looks to planeswalkers to generate card advantage, so in addition to Nahiri, the Harbinger we find Chandra, Torch of Defiance--great in a control deck without counterspells--Gideon Jura, and Gideon of the Trials. Since they also serve as win conditions, there's no need for any creatures beyond the singleton Emrakul, so the deck is great at blanking opposing removal spells, thereby gaining virtual card advantage.
We're used to seeing the deck not play Path to Exile or Lightning Bolt due to the presence of Chalice of the Void, but without the artifact this list list is free to upgrade its removal suite. Still, the pilot has opted to leave the one mana removal in the sideboard and instead maindeck the removal that gains life and various sweepers to help clear the battlefield for the planeswalkers.
Using half the sideboard space for minor upgrades in removal is strange, but I don't mind having the more powerful removal in the main. I especially like the singleton Urza's Ruinous Blast, a very powerful sweeper that leaves planeswalkers around, even if it plays awkwardly with Blood Moon and Cast Out and is fairly expensive at five mana. It's a card that will win games that no other card can, so the first copy is quite valuable.
Having so many removal spells can give you awkward draws against other reactive decks, so Nahiri's rummage ability is very important here as a means of artificially increasing the deck's threat density. It really is the card that pulls the deck together, and while we haven't seen it play such a central role in quite a while, I think it's up to the task.