The Bloodmarch, page 12:
“Some claim to have traveled under the mountains from the Bitter Reach to the Bloodmarch, using an old dwarf settlement called Järnhem northeast of the Bloodmarch. The tunnels are supposedly connected to Belderand and offer underground passage to the Bloodmarch from the icy Winding Ways of the Bitter Reach as well as from the misty mountains of Ravenland.
Whether these stories are true or not is highly unclear as most dwarves will not say a word on the matter.”
PLEASE PLEASE PLEASE MAKE THIS TRUE!!!
A book of a vast subterranean labyrinth would be the perfect next Forbidden Lands supplement.