THE CARD
Name: N'kai
Set: MSGS
Type: Location
Region: Exotic Location
Location Attributes: Country, Underground, Artifact, Tome
Public Attributes: Outside
Gate Attribute: Yes
San: -2
Unique: Yes
Special Effect Box: You may play this card only if your Current Location is Underground. You must walk out of N'kai. While at N'Kai all Monsters in your Threat function as if it is Night.
THE SOURCE
"[N'Kai:] A black realm of peculiar-sensed beings which had no light at all, but which had had great civilisations and mighty gods before ever the reptilian quadrupeds of Yoth had come into being."
From "The Mound" by Howard Lovecraft & Zelia Bishop
Lovecraft first told of N'Kai in "The Mound", a story he ghost-wrote for Zelia Bishop. It is a great black abyss, deep within the Earth, below the unearthly realm of K'n-yan, below even cryptic Yoth. When the god Tsathoggua came to Earth, he first dwelled in N'Kai for a time. Today, his Formless Spawn still live there, worshiping the toad god's statues. Most gates to N'Kai are sealed, but those who can read the ancient Yothic manuscripts can still learn of its horrors.
CLARIFICATIONS
Because N'Kai is in the Country, you must walk to it. You can't use a Car, Train, or other mode of transportation because of the stipulation "You may play this card only if your Current Location is Underground". Whenever you play a Travel Event, it goes to the top of your deck, and becomes your Current Location. Thus, by the time you're ready to play N'Kai (even if you just played a Car), your Current Location is not Underground, and thus the play is illegal.
Note that N'Kai places no stipulations on where you must exit to. You must walk, but can go to any subregion or region in your current Dimension. The Location you're walking to doesn't even have to be Underground. You could enter N'Kai from Pickman's Apartment, and exit to The Office of Dr. Freud. This, of course, doesn't override regular restrictions on Locations (ie, you couldn't exit to Celeano, which requires you to Travel through Space).
Like all Exotic Locations, N'Kai is unharmed by Spells and Events that affect the top card of your story deck. This means it can't be hit by Cthulhu Rising, Wave of Oblivion, or any of a number of other things which bury, discard, destroy, or otherwise directly effect your top card. However, it can be indirectly effected. You can, for example, cast "Create Time Warp" while in N'Kai, and thus put another card on top of it. You could also use Create Time Warp to move N'Kai to the top of your Story Deck, since the Special Effect Box isn't used until after N'Kai has already been made the top card. Likewise, Artifacts such as the Sphere of Nath can affect N'Kai.
Note that even when you are walking to N'Kai, it's safe. This is because Exotic Locations are protected when they are your "top card", which is defined as "the card at the top of your Story Deck, which may have any Orientation".
QUESTIONS
Q: Is N'Kai really supposed to be "Outside"?
A: Yes. It's big. Really big. So hugely big that you can't even imagine how big it is.
Q: What happens if I have a DREAMLANDS Fireworm in my Threat, which makes all the Monsters in my Threat function as if it is Day, but I'm in N'Kai?
A: All Monsters in your Threat function as if it is Day. The primary rule for resolving card conflicts in MYTHOS is that the last card played has the dominant effect. By extension, if a Spell is cast after something else, the Spell has the dominant effect, and if a Monster is revealed after something else, the Monster has the dominant effect. In this situation, N'Kai is already in play, and then the Fireworm is revealed. Since their powers conflict, the Fireworm wins.
Q: What happens if Tulzscha is out and I'm in N'Kai? Do the Monsters in my threat function as if it is Day or Night?
A: They function as if it is Night. N'Kai says "all Monsters in your Threat function as if it is Night". Tulzscha says "It is day". These effects do not conflict.
Q: Can I walk from N'Kai to an Island?
A: No. The standard rule for Islands, as of MSGS, is "You can not walk or use Travel By Land or Travel by Air cards to go to, from or between Islands, unless Special Effects say otherwise." Nothing on the N'Kai card directly overrides this. Alas.
STRATEGIES
I'm a bit hestitant to offer strategies for N'Kai. The problem is that it's Unique, and it's a Location. This means that it isn't going to show up a lot. However, if you use the following strategies while you have N'Kai around, sometimes you'll end up better for it.
Unstoppable - All Exotic Locations have an identical advantage. They can't be buried or discarded by Spells of Events when they are your top card. You can turn this to your advantage to complete adventures. If you have an Exotic Location in your adventure, save it until last. About the time when people are thinking that they should stop you by Discarding something, they probably won't be able to. You may even want to use an Exotic Location if you don't need to. With N'Kai, for example, you could fulfill the Country/Gate requirement of an Adventure, and know it probably won't be blasted away. It's also advantageous to have an Exotic Location as one of the requirements for summoning a GOO, since people probably won't be able to destroy it even if they realize what you're up to (ie, you can use N'Kai to help summon Tulzscha, Abhoth, Hastur, Ghatanathoa, Nyarlathotep, or Nodens). Don't make it your only Location, since all Exotic Locations in LIMITED and MSGS are unique, but have it around as insurance.
The Monster Bash - N'Kai is a nice place to summon Monsters. Dimensional Shamblers are +1 because it's an Exotic Location. Skeletons, Vampires, and Zombies are +1 because it's effectively Night. LIMITED EDITION Dholes are +2 because you're Underground. DREAMLANDS Ghouls and Gugs are +1 because it's Underground. Since the N'Kai gate isn't reusable, you need to have the Create Gate spell or various Summon/Control spells to take full advantage of this. Using Create Gate to get out Joined Monsters is the best, since otherwise you're paying 1 Sanity, to typically get 1 Sanity of extra damage.
The Magical Mystery Tour - N'Kai can be used as a somewhat inconvenient but vastly cool way to get from one Region to another, particularly between Lovecraft Country, Europe, and the Middle East. It's also almost impossible to stop (even more so than U-Boats).
An Easy Exotic Location - Of all the Exotic Locations in print up to DREAMLANDS, N'Kai is definitely the easiest to get to. You just need to walk there from one of a number of Underground Locations you can stack in your deck. This starts really being an advantage with DREAMLANDS, which has one adventure that requires you to journey to a (generic) Exotic Location, and has an Artifact and a Tome which can only be found at Exotic Locations. There will be more Exotic Location specific items in the future too, so expect this advantage to grow. In addition, remember that each Exotic Location forms its own region. Thus, if you walk down from Pickman's Apartment in Boston to N'Kai, you've suddenly fulfilled the requirement of visiting two regions, without having to go through the bother of boats or planes.
The GOO Deck: Take one pinch of N'Kai, and a handful of cards from some region (any will do, Europe, the Middle East and Lovecraft Country all have Underground Locations). Add in The Strange Case of Charles Fort. You've now got all the reqs to summon Ghatanathoa, Hastur, Abhoth, and Nodens. Throw in a sprinkling of New Moons, Nyarlathotep, Dholes, and Dimensional Shamblers for additional fun. You'll need another adventure or two too. And, you'll want a few more Underground or Country/Gate Locations. Seeking Everlasting Life 1 and Seeking Everlasting Life 2 are my first choices for additional adventures (22 points).
COUNTER STRATEGIES
Destroy in Advance - Most of the time, you can see when someone is heading towards an Exotic Location. For example, with N'Kai, your opponent has to play an Underground Location first. That card can be destroyed, as long as you catch it before your opponent plays the Exotic Location.
Destroy with an Artifact - Exotic Locations are proof from Spells and Events, but not Artifacts. Though the Sphere is Nath is expensive, it can destroy Exotic Locations.
Keep Sanity Low - All Exotic Locations have high Sanity requirements. If you keep your opponent's Sanity low, he won't be able to play them.