|The Fourfold Catatomb|
What does the dungeon look like? Geometric, symmetrical, finely made and richly carved. Obviously, no expense was spared to make it and slaves were worked to death to ready it. There might be hidden niches, scrawled graffiti where it couldn't be seen, places that were sabotaged by the workers themselves. However, most of the dungeon is rich, carved and well made. Much of the treasure in such a dungeon would be in the form of carvings, friezes, wall-hangings and so forth. Places might have decayed over time, been flooded or otherwise, but the overall feeling should be rich, and possibly oppressive and over-awing, with large statues of the monarch.
What are the monsters? Well, this is where my imagination usually runs off with me. Basically, the dungeon was stocked with protectors for the monarch - undead made from enemies of the state. These would be the afore-mentioned bronze-corpses, wood-walkers, bone-banes and lilting-weirds. These are probably more-or-less mindless undead or combinations of automatons & undead, powered by the souls of the king's enemies. These would be a generic menace to adventurers entering the dungeon, but something that could also be turned or subverted to help - or at least ignore - the cunning adventurer. A simplistic approach would see looters trying to wade through ever larger hordes of them, possibly dying pointlessly. On the other hand, the crystal-and-blood creations are sworn protectors of the dead monarch, implacable foes of looters and a combat trial that has to be faced to win riches or avoided. The bone-and-wax creatures are there to provide pleasure for the monarch, these would be used more to give a sense of horror and the macabre to the dungeon than to truly be foes for the adventurers, though they might overcome weakened characters. Finally, should the characters come upon the resting place of the king himself, a fitting end would be to have them face the "four ancestors" - perhaps demons bound to the king's body, who had empowered him to raise the kingdom.
In a final twist, the demons might actually be waiting for somebody worthy of them and they might offer one of the adventurers the temptation of taking their gifts (lets say of a silver tongue, a mighty hand in war, eyes in the back of the head and a ward against physical attacks) and reclaiming the lands the king had ruled. Perhaps the king was an unwitting pawn, perhaps he had played the demons for fools, in any case, this gives an open ending - instead of just going for the treasure, the heroes might unleash further adventures.
And there it is ... a self-contained, wealthy, maze-like tomb, filled with macabre soul-powered automatons, dolls and corpses, centred around a quartet of powerful demons. Add a dash of jellies, oozes, gelatinous dodecahedra, perhaps some worms or rats, and voila. Serve properly dried and diced!