As the portcullis closes behind you you can see the skyline of a squat city in a massive cave,. There is a light blue phosphorescent glow over everything, but it is still very dark, you have visibility out to about 100 feet through darkvision and the glow.
There is a massive natural cut staircase before you 30 feet wide that steps into the chamber. To your right a cut rock incline for carts to enter and exit and at its base 2 fountains shaped like mushrooms spraying water into the air.
You can see that most buildings are 30 feet high, but there are 3 natural rock towers that reach upward, most likely connecting with the ceiling with is lost above in darkness. The towers have windows cut in them lightly glowing, so you know they are hollowed out and gnomes live in them.
You can see dozens of gnomes scurrying about, wagons pulled by spiders or lizards and gnomes riding on lizards, the city is bustling with activity. All the gnomes eye you suspiciously, some stopping what they are doing to gawk at you
Off to your left is a massive tower with banners around it, it looks to be sitting on a plateau with a natural ramp rising to its human sized front entrance way and doors. Dozens of armed gnome guards dressed in chain-mail stand guard around it. It must be the palace….
The guards scrutinize your writ of passage, but you are eventually let inside. The tower is indeed hollow and you enter a oval room which looks to be most of the interior of the tower. In front of you a gnome with a long grey beard sits on a throne of polished jade. He is flanked by a couple dozen armed gnomes holding short pikes
Behind him twin staircases rise to a small balcony above the throne and then continue on to a larger balcony which rings the whole room. You can see movement up on the balcony, there are more guards up there.
Tiberious who speak the language of the deep gnomes approaches “Hail lord Greybeard” who answers “The biggest pair you’ve ever seen travelers”
Greybeard: What brings surface dwellers to my kingdom?
Tiberious answers truthfully about seeking the teleport as well as trade.
Greybeard: You are looking for the stone that controls the teleport? I do have it. It is kept secure, for that teleporter leads to a dangerous place. Why do you want it?
The party continuous truthfully then Greybeard explains that it leads to an evil place. He would not give it up but would let you use it. He woudl send a contingent of gnomes with you, they would hold the teleport spot for your return. Or meet you at predetermined time.
He explains that long ago a group of wizards created these portals to travel between the surface and the underdark, they can also move between the teleporters to get around the surface and underdark.
There were armies of evil creatures in the area that “his” teleporter leads to. The gnomes hold the stone to ensure those creatures do not get down here. But they have not used it in ages.
The party is forthcoming about their run ins with Drow Druegar and the Illithid ‘Zarlag’ and how the head of the house NOQUAR is now deceased. Greybeard has no love of the Drow and thanks you for your service, and explains the power structure in this area……