Last time, the adventurers found the ruins of an underground complex that could serve as their new base of operations.
This time, they explored those ruins and discovered, among other things, a large, lightning-fast serpent hiding out in one of the chambers. They managed to slay the creature, mainly via Klag’s deft badger-style combo attack. Then they discovered it was actually a mechanical creature. It was not a cyborg, like the megafauna, but an entirely artificial construction. It must have been a left-over feature of whatever the complex was in its heyday.
After that, they explored the rest of the complex, and found metal crates, “sun wheels” (gears), and dolls decked out in bizarre metallic jewelry. The sun wheels and jewelry quickly became symbols of their new tribe.
Last, scouts returned from the surface with urgent news of an attack by a horde of intelligent sea scorpions. The adventurers quickly devised a strategy: they lit a fire at the entrance to the complex’s atrium to obscure it from the approaching creatures. Then they stationed themselves on a level above and waited. As the sea scorpions advanced through the smoke and into the atrium, they launched their javelins while the adventurers rained hell down in the form of arrows and sun wheels. In particular, they lobbed the largest, heaviest sun wheels onto the weakest part of the only stairwell leading up to their position. Eventually this weakened the stairs until they collapsed, killing many sea scorpions in the falling rubble.
This was enough to route the attackers, but who knows for how long?