At a generic level, read my dungeon building advice.
http://www.enworld.org/forum/showth...crawling/page3&p=212975&viewfull=1#post212975
So, apply that to your specific situation.
a) You've left the god of trickery and his demon generic. Don't. Understanding what worship was about is critical to creating your dungeon. You've hit a road block in your creativity because you're not addressing the critical issue. What things are associated with and symbolize this deity? What animals does the god have some dominion over or relationship with? What creatures? What plants? What beasts - foxes, ravens, coyotes, monkeys, snakes, etc. - might have moved into the area with the deities approval?
Well, actually, I just didn't feel like adding a lot more info to the original post, but since you bring it up....
Mikar: god of the underdark, evil emotion, treachery. Twin brother of Mikol, sometimes worshipped as his second face rather than a separate being. As Mikol is the sun, Mikar is the moon. Most of the goblinoid races follow Mikar.
Alignment: Chaotic (many worshippers are evil, but some are neutral, and a rare few are good)
Domains: Darkness, Evil, Madness, Orc, Retribution, Sloth, Strength, Trickery
Weapons and armor: any/any
Colors/symbol: black and red/ a black mace
Animal: rabbits and cats
Mikar frequently allies with "lesser" demons who are attempting to prove their status; in this case, a powerful demon who had recently been defeated by his own enemies who was interested in rebuilding his strength and followers. Together, they sought to overwhelm a small, newly formed kingdom by infiltrating it with their own priests and eventually usurping the rulership. They failed when they moved too quickly, their main temple was exposed, and the good kingdom's armies met theirs on the field of battle, decisively defeating it. Or at least it SEEMS they were decisively defeated...
b) What needs were the builders of the temple trying to address? If for example the god required animal sacrifices, then there was probably some sort of area near the entrance where livestock could be brought, kept, and perhaps sold and traded. The temple also probably needed a water source, so their was probably a well or possibly a spring and probably a building to contain and protect it. The temple probably had full time laypersons to maintain the temple and the grounds. Where did they live? What was their status - monks, servants, slaves, prisoners, etc.? If they weren't here willingly, some sort of overseer probably had to manage them closely. The temple if it feared attack may have been fortified, with the grounds surrounded by a now largely broken down wall. What other out buildings might the temple have needed?
The temple was in a fairly isolated area, on the flanks of a newly resettled region that was growing rapidly into a wealthy and strong new kingdom. Mikar does love sacrifice, but mostly of things a person treasures - so I suppose there would be sacrificial altars in the main temple, offering bowls, and perhaps even "wishing pools" into which valuables could be cast. That's the sort of thing I need!
The village ten miles from the temple ruins in the present day was the main source of lay workers; they were thoroughly dominated by the temple in the old days. Yes, the temple would have been fortified, but most likely with a wooden wall; stone is not uncommon, but the temple was secretive enough that they would not likely have had the desire to build a large defensive wall; construction projects that size draw attention!
This was a moderately large temple, but secretive, so they tended to skimp on extra buildings; they had some underground barracks and cloisters for the priests. The bulk of their "army" was goblins and mercenaries who could be required to camp and to move frequently to preserve secrecy. Then again, they probably did have SOME outbuildings; I imagine a half-dozen or so structures, whose purpose now is pretty obscure.
c) In what ways was the temple serving the community? Someone paid for, built, and worshiped at this temple. Why? Who was petitioning the god of trickery and for what purposes? Why did the local population think it wise or important to build this temple? What wisdom did the temple teach? Were classrooms required or lecture halls? What did the temple sell? For example, might the temple used its knowledge to monopolize production of subtle potions and poisons?
This temple was a military headquarters, and also controlled the local populace. They trained priests here to go out and infiltrate the newly forming kingdom nearby. They came from outside, from another kingdom not far away, in which Mikar's hated twin god Mikol is dominant. They found this valley, which boasted several good-sized villages but was only lightly protected. They quickly moved in and took over by slaying the baron who had claimed the area (but who had not sworn fealty to the local king). The local populace was sort of taken by surprise and absorbed before they realized what was happening. However, since the priests and their army were able to offer them better protection than the baron had, they acquiesced fairly quickly. Mostly they were not completely willing followers, but within a generation, resistance had faded.
The temple definitely would have had lecture halls and classrooms. Not so much generation of any materials here, though; there are better places not far away to find things that would make poisons and potions; they're only a hundred miles from some really deep swamps and bayous. Instead, newly ordained priests and likely recruits would be sent here for indoctrination and instruction.
d) What changed about the relationship with the local population that caused the temple to be destroyed and more importantly abandoned. What services that the god provided either stopped or started to come at too high of a price?
The temple was destroyed when the small nearby kingdom realized they were being infiltrated, and made a concerted effort to find the source of the infection. They discovered the temple, recruited some allies, and rode out to wipe it out. They met in battle and defeated the evil army. Or at least that's the story that is told. It might be that, realizing they had been discovered, the evil forces put up a strong defense just long enough to get their core leaders and resources away from the temple, then allowed it to fall so they could go deeper into hiding elsewhere. You know how that goes!
e) In 100 years, lots of vegetation, even a whole forest, could have grown up in and on and around the temple. How does this disguise the original purpose or interfere with motion. Early succession plant life typically includes brambles and thick groves of evergreens that could block line of sight and create difficult terrain - forcing perhaps crawling to reach inner areas. Vines, ivy, and mosses likely now grow over the stone work. If the area is a reservoire of evil, many of these plants are likely unpleasant in some fashion even if attractive - poison ivy, poison oak, poison summac, shelf fungi, poisonous mushrooms, nightshade, black locust, wolfsbane, etc. On the other hand, some of these might be worth something as reagents or alchemical supplies if recognized and carefully collected.
Yeah, nasty things like poison plants will be present. I'll need to do a tiny bit of research to find out what would be most common in the climate/region, but that won't be hard. Moss, ivy, spanish moss, etc... should be plentiful. Thanks for reminding me to generate this info.
f) You mention scavenging materials and disaster. What was scavenged and what resulted. What evidence of the scavenging remains.
g) What else has over the years investigated the temple, and with what results? Did monsters try to tunnel in the area? Who might have taken advantage of the temple's isolation? What external evidence might monsters living in the dungeon (if any) leave on the surface? Have former adventuring parties ventured into the temple? How far did they get before abandoning the task? What evidence did they leave behind? What tragedies might have happened over the years?
I think these can be answered in one response; there's not much evidence of scavenging, because it always ended in quick disaster. One creature I KNOW is present on the surface is a pair of caryatid columns who attack anyone who tries to carry anything away from their section of the ruins. So there are a few mangled corpses from 80 years ago, now nothing but skeletal remains, crushed and weathered.
I'll need to see what the surface evidence of monsters underneath would be - that's a great suggestion. I know there are spiders and beetles and giant rats; rats especially might easily have ways up to the surface - in fact they'd really HAVE to.
I'll also make sure to have one area where an adventuring party in the past tried to dig their way down into the catacombs below, but met an ill fate. That will scare the PCs! As far as the actual temple underground entrance, if there was sign of earlier explorers, it has been disturbed and removed by the current "expedition".
