The party discovered that the dark rider was captured by the Skum and taken into their underwater home under Lake Illmarsh.
They took Horace Croon’s submersible down and on the way they were attacked by a Giant Octupus and a spell casting devil fish. The battle was difficult but they ended up defeating both creatures.
After reaching the bottom they went through a force screen keeping the water out of the tunnels and into the Skum’s home.
There they fought plenty of Skum’s, a giant spell casting mushroom, a Gug, and these alien insectoid creatures known as the Mi-Go.
After several difficult fights the party rested in a cave, where they were attacked by 2 Leng Spiders which were defeated.
Know full rested, they go to see what else lies inside of the tunnels and what awaits them in the metal dome they saw from outside.