This adventure is made for classic treasure hunters with few stiff fights. The rewards are high, and the traps lethal.
The Kingdom of Melethad was quite small, and nestled in a remote mountain valley. It boasted little natural resources apart from very rich diamond deposits. Its wealth and formidable natural defences kept it aloof and safe from its enemies.
However, its location was also it’s doom. A vast glacial lake had been building up for centuries, and in one final catastrophic release, flooded the valley, washing away all virtually all of their works and drowning the people.
Not everything was lost, however, for beneath Castle Melethad was a strongly built dungeon, home to a massive vault used to contain the realm’s treasures, including a massive store of diamonds.
Freed by the break, a river filled the valley, further hiding what once was a thriving kingdom.
Now, several generations have passed. Some still speak of the diamonds of Melethad, but many dismiss them as folk tales.
The river has diminished greatly in size, and some treasure hunters have come to the valley, seeking the vast treasure somewhere under the sludge.
The PC’s have come into the employ of an Astrologer who claims to have enough information to pinpoint the ruins. He needs muscle and skills at dungeoncraft, for the vault was well protected.
The Astrologer in turn has been hired and is sponsored by a petty nobel whose lands are somewhat downstream of the Drowned Realm. As a result this expedition will be reasonably well funded.
Room One: Entrance and Guardian - There needs to be a reason why your dungeon hasn’t been plundered or why your adventurers are the ones for the job.
The Drowned Realm
The Astrologer has been carefully sighting the nearby mountains and has walked very deliberately into the middle of the muddy plain. He stops and reaches down into the muck. "Worked Stone! I’ve found it!"
A bit premature - he found part of the ruin, but it may take some time for the PC’s to find the stone portal leading into the lost castle’s dungeon. As much time as desired by the GM may be taken to find and escavate the entrance below.
The dungeon below the castle is large, but not a maze. The Astrologer knows the layout well enough to bring the PCs to the First Door easily enough.
Complication: Rival treasure hunters may seek to claim jump the PC’s. The threat should be serious, but not overwhelming.
The First Door
Room Two: Puzzle or Roleplaying Challenge - A trial that cannot be solved by steel alone.
Meant to require many hands to open and thus rule out sneak-thieves and the like, the door weighs many tons and must be lifted. Several large metal eyelets for inserting beams are worked into the massive door.
No automatic mechanism exists - enough strength must be brought to bear to dead lift 5 tons. Back in the day, when the door was opened, pulleys were fitted into sockets in the ceiling (the sockets can be found upon searching, but the pulleys are absent) allowing fewer men to be used to open the door. The door does not lock in place, and so must be held up while other crawl underneath. 10000lbs will crush anyone unfortunate to be caught underneath should it be dropped.
Complication: The dungeon is still flooded in places. As a result, 2’ of water covers the floor, making it even more difficult to lift, as the eyelets are underwater.
Room Three: Trick or Setback - Build tension through tricks and setbacks and give them a double-dose of gameplay such as more combat or another roleplaying challenge.
A 40’ hallway, 5’ wide with 7’ ceiling. Every 10’, the ceiling lowers down 1’ requiring stooping and crouching.
The hallway was once heavily trapped, but the length immersion has ruined many of them. The floor is littered with pressure plates that will click when stepped upon, but little will happen. The first and last pressure plates are 4’ long and the width of the floor, and form the only trap still working. If the last pressure plate is activated while no pressure exists on the first, a stone slab 4’ long and as wide as the passageway will drop into the hallway. It is 6’ thick and blocks the passageway completely when it falls. It weighs roughly 10 tons and does not automatically reset - it needs to be lifted back up into the ceiling manually.
Complication: Like the door, 1-2’ of water covers the floor, making detection of the pressure plates difficult at best.
Complication: Other traps just might be still viable.
The PC’s are not there yet! The last obstacle is a massive bronze door with 6 large keyholes. All must be picked or magically opened separately in order for the door to be opened. Even unlocked, the massive portal requires signficant effort to open. What lies beyond?
Room Four: Climax, Big Battle or Conflict - The final combat or conflict of the dungeon.
The vault was not 100% watertight, and many of the valuables within the room have rotted away. All of the chests have been rendered useless, their traps defeated by time and water. A trove of diamonds and precious metals remain. But, they are not undefended. Bronze automations of various sizes and types have survived the immersion and will rise up and attack the pcs, for non save the long dead and drowned king can enter unmolested. The fight should be dire…
Again, this room could be partially flooded, putting most of the treasure below the murky waters, along with the guardians.
Room Five: Reward, Revelation, Plot Twist - The dungeon is complete but what is it about this dungeon that made it different or memorable. What kind of mystery have they discovered, what kind of reward have they won, and what kind of information have they recovered?
And it does not end with the mechanical foes.
The Petty Noble who sponsored the expedition is not interesting in sharing the booty. It was his ancestor who engineered the flood that devastated the kingdom. They did not anticipate that the region would be under water for an extended period, so the plan bore no immediate fruit for it’s instigator.
He has followed the PCs to the location with a large force and will wait until the PC’s emerge laden with treasure to attack. If the battle with the constructs was taxing, fighting the nobles troops should be even more so.
Complication: The spirits of the village have not rested. With the coming of the Petty Nobel to the valley, they have their chance at revenge. They will release a second flood into the valley while the fight is ongoing. The PCs might get some warning of this, either subtly - a rumbling, or explicitly from the spirits ("Run Mortals!", whispered unseen into their ears).
Complication: A third force of claim jumpers of any desired makeup turns the fight into a 3-way combat.
The desired end result is that the PCs barely survive and managed to obtain at least a reasonable amount of treasure before being forced to flee by a second flood. Now that the portal was open, the waters will destroy even the dungeon, and the remainng treasure scattered down the river. Panning for gold and diamonds will become a popular pastime down this river.