In the Darklands of Golarion, there are three regions. The uppermost one is known as Nar-Voth; this is the "wilderness" of the Darklands. The races who live here are relatively isolated, tribal, or small. The duergar are an exception, of course, but that's only because they have a bunch of abandoned pre-made dwarf cities to squat in. Below Nar-Voth lies the largest realm—Sekamina. This one's the classic underground warren of tunnels that span continents that long-time gamers will find the most familiar. The drow are the primary race here, but there are others like the skum, the serpentfolk, ghouls, and morlocks.
Then there's the third realm. The deepest realm. This is where we transition from the classic underground RPG realm back into the pulps, for the most part. In this realm, known as Orv, there are many immense caverns known as Vaults. Golarion doesn't have a Hollow World or an Edgar Rice Burroughs style Pellucidar per se, but these vaults are big enough to stand in for those regions. Underground oceans, caverns with jungles and artificial suns, entire nations of warmongering humanoids, and regions containing mountain ranges and vast deserts but deep under the earth dominate Orv, and the denizens of the upper Darklands think of the vaults with the same sense of fear and wonder that surface folk do for them. Orv is sort of a Darkland for the Darklands.
Into the Darklands covers the races and major locations for all three of these realms, but of the three, it was Orv that I was the most excited to see come alive. The enormous lost worlds of deep underground are a classic trope of the genre, but not one that's been done all that much in the game. Certainly not much in Pathfinder until now; we've had our share of big dungeons and cave systems already, but now? Now it's time for immense underground deserts ruled by undead drow, dinosaur-infested jungles where cavemen and troglodytes squabble over the best (and safest) places to live, and oh yeah... areas ruled by classic monsters like intellect devourers and giant worms!
