It appears that Forbidden Mountain was once used as a mine by an ancient civilisation. Inside the mountain is a sophisticated old cave system full of extensive tunnels apparently used to mine a strange rust-coloured mineral. There are remnants of crates, mining tools and ingenious pathways through the mountain with well-placed defensive structures.
In more recent times, the mountain was home to a hobgoblin kingdom, which consumed all of the ancient mine’s resources and then filled it with booby traps to prevent trolls from accessing the hidden pathways. The hobgoblins abandoned the mountain some years ago although their traps and warnings remain.
Although Forbidden Mountain now appears derelict and abandoned, there are still some creatures living inside. While it provides a way of approaching Troll Mountain without being seen, it is a dangerous route to take.
The entrance to Forbidden Mountain lies in the grey and rocky foothills of the Black Mountains. A path to the east ends at a large stone doorway set into a rock wall. The doorway is signposted by two posts with impaled troll skulls. The frame of the doorway is covered with glyphs and runes, relics of the ancient civilisation that first built the mine in the mountain.
Inside Forbidden Mountain is a series of dark tunnels and immense stone caves cut out of the rock. Rusty manacle-rings line the walls, possibly where slaves were chained while they mined the rust-coloured material from the ground.
The narrow tunnels and mine caves eventually lead to an enormous cavern filled with a broad subterranean lake. The water in the lake is a thermal pool and consequently steaming hot. The lake is spanned by a low bridge that leads to a stone path cut into a 300-foot rock wall. The path up the wall passes two guardhouses with drawbridges. Past the last two-storey guardhouse and drawbridge at the top of the path is another stone doorway that marks the exit from Forbidden Mountain.