Really cool interaction I found while running Narfi, Betrayer King and Nissa of Shadowed Boughs in another sultai deck, if you are running all snow lands then Narfi buffs them up to create some potent damage threats. This deck is all about using Avalanche Caller, Narfi, and Nissa to deal significat damage to the opponent using our snow lands. Scuptor of Winter is a nice include as its buffed by Narfi due to it being a snow permanent but also allows us to untap our snow lands to ramp into our mid game threats. The Three Seasons allows us to fill up our graveyard and return any snow permanents we might need to our hand, be it a land or Avalanche Caller or Sculptor of winter. The Three Seasons also allows us to place key cards back into our deck after its third counter and can slow down opponent's graveyard threats in a pinch. Tymaret Calls the Dead is also another graveyard filler that can create some zombies for good board presence and in combination with The Three Seasons can allow us to potentially drop Narfi down on turn three or four for three snow mana.

Graven Lore is something I threw in since this deck could use some form of draw and it synergizes with the fact that we're using our snow lands as a resource. Along similar lines, Priest of the Haunted Edge is a nice include that helps protect against small aggro threats while also using our snow lands as potential slow removal while simultanously being buffed by Narfi. Murderous Rider is just solid removal and more synergy with Narfi and what I think is a bit of a sleeper card is Jarl of the Forsaken. Foretelling this card and then being able to remove a big threat if an opponent's creature or planeswalker takes damage is highly underrated. Plus you can flash it out for added board pressence and it fits the theme of buffed up zombies/snow lands. Faceless Haven is another include that can help close out games and creates even more mid range threats in combo with Narfi. 

Overall a really fun deck that will definitely make your opponent go "Wow, that was actually pretty sick!" especially when you drop Narfi from the grave for three snow mana at instant speed to pump your board. I just love Narfi that's all ;)

EDIT: Still tuning the deck to make it more playable against some of the meta junk that's out there. I've been seeing a lot of artifact and enchantments rolling around so added Wilt for some okay hate. As much as I like Priest of the Haunted Edge, Heartless Act is probably just better and faster. Toned down The Three Seasons for one extra Tymaret Calls the Dead, felt like the deck needed more board presence. Also removed Jarl as even though its fun, again its just a bit too slow against more aggressive decks. Added Zagoth Triome for some better mana base. 

EDIT 2: If you like this deck and have the collection or Wildcards to take to Historic, my Historic Sultai Snow Lands is also GAS!

https://aetherhub.com/Deck/historic-sultai-snow-lands