KB1 is short for Krephus Bore One. It is a location along the Krephus Passage where the primordial worm Krephus decided to bore straight down. When the region around was properly mapped, it was concluded that Krephus made the decision to dig deeper because of natural obstacles. She was hemmed in. In the north she was blocked by the waters of Morwuld Briin and in the east by a river of elemental earth known as the Earth Seam.
Krephus Bore One goes straight down for three thousand feet. At the bottom, now in Hezmort's Tier 2 Underdark, the Krephus Passage heads north under the ocean.