The Millenia Cave
Located near Willowshire, The Millenia Cave is a cave that was used by a group of smugglers-turned-cultists.
The relevant session can be read about here: 5.2 THAT DEMON PLAYED YOU LIKE A FIDDLE!
Just inside the cave is an alchemists lab.
Opposite it is a wooden suspension bridge with huge spikes below.
Past the bridge is a whirlpool that could be used as a shortcut to the storage area south of the alchemists lab.
Continuing south from the whirlpool, there is a large room of stalagmites and stalactites.
Past them is a corridor of reddish-brown mushrooms.
The end of this corridor exits to the storage area.
The small path just opposite the storage area leads to an area once filled with swarms of spiders and Sheila, a huge spider queen.
South of the storage area is a path leading eastward into an area with more mushrooms and some long-dead corpses, seemingly having succumbed to the acidic mucous produced by the mushrooms above.
Further east is a large space dominated by an evil ritual circle and prisoner cell.
Southward from that leads to the scorching molten lava river with chains and islands held up by stone hands.
Following the river westward leads to a hidden enclave, inside which is a staircase leading upwards to a small room.