NOTE: The following contains SPOILERS. If you are playing in this adventure, stop reading NOW!
The encounter states the following about Lareth and his motives:
He has been sent into this area to rebuild a force of men and humanoid fighters to gather loot and restore the Temple of Elemental Evil to its former glory. Of course, Lareth is but one of many so charged, but he is looked upon with special favor and expectation. He and his minions have been careful to raid far from this area, never nearer than 3 or 4 leagues, traveling on foot or being carried on wagons of the traders from Hommlet. None of the victims are ever left alive to tell the tale, and mysterious disappearances are all that can be remarked upon, for no trace of men, mounts, goods, wagons, or draft animals is ever found.There are some interesting tidbits in this description. First and foremost is the fact that Lareth is not the only Temple agent in the area recruiting and raiding, only the most favored. As such he is probably spied upon and watched by those higher up the chain of command, for Chaotic Evil masters are constantly looking over their shoulders at their servants. Being a 5th level cleric puts him pretty high in the Temple hierarchy as well. There must be other, lower level agents nearby that are assisting him and the Temple. I'm sure that a recruiter is working on acquiring humanoids in the region. Also we know that there are spies working in Hommlet - at the keep construction site, the Traders, and in the Inn - all of whom must report to Lareth since his location is the closest and he is in such good standing. It is noted that the Traders correspond via brigand courier, so there must be quite a few people passing through the village on a daily basis, enough for a rough-and-tumble brigand to move freely without being recognized or questioned by anyone. I assume that the village guards are not ALWAYS located at the tower of the mayor - there must be some interaction along the main road with people, especially if the "old problems" have returned to plague the area. Also, note that the placement of the tower along this road is not simply convenient, but shows that the danger comes from this route.
Also, assuming that the other evil agents are based in some sort of camp - either as bandits, or as character types - means that the players could run into more places like the moathouse, perhaps akin to the bandits in the tower at the Temple grounds. Any number of abandoned, run-down farms, old toll houses or burnt inns along the roads and trails could house these miscreants. By keeping these encounter numbers low, the DM could build up the moathouse as being a more likely place for evil to base itself. Clues found at these sites might also lead the players to the moathouse. Nulb is listed in the module as being 6 miles distant. All other large distances in the module are given in leagues. I believe that this number is mislabeled and should read as "6 leagues" to make the distances match better with the later T1-4 descriptions written by Gygax in part 2. This puts the Temple roughly 7 leagues away from Hommlet - close enough to be a menace but far enough away to be out of sight and mind for the most part. This would put Emridy Meadow somewhere to the north and east of Hommlet which makes sense according to the descriptions provided. According to the WORLD OF GREYHAWK maps, this places Hommlet at the border of the hex southeast of Verbobonc, and Nulb and the Temple in the next hex northeast of Hommlet. This area can still be regarded as hilly and forested due to it's proximity to the Kron Hills and the Gnarley Forest without being considered as part of those areas.
Since the track along which the moathouse is located is no longer in use (the module states that it is overgrown and needs to be cleared the first time to make it passable), it is assumed that Lareth's raiders strike along the eastern "High Road," at the stated 3-4 leagues away from the moathouse (which is located only 1 league north-northeast of Hommlet according to the original module text). A league = 3 miles = the distance a man can walk in an hour. So, the raiders are striking targets 3-4 hours away on foot, but probably even closer since the marshy terrain probably slows them to half speed, so we're talking 6-8 hours tops. A far raid of 4 leagues away might require the raiders to camp outside the moathouse for the night, making them vulnerable to detection. Since the loot is obviously not being stored in the moathouse, it must be going to the Temple, probably along with new Temple recruits. Since the Traders are obviously in on the raids (according to the statement that the raiders sometimes are carried in their wagons) it is safe to assume that some of the items stolen might make their way into the Trader's stock. This provides a DM with a way to link the village with the Temple and possibly give reticent player characters a reason to investigate. Assume that a piece of merchandise is actually uniquely traceable, perhaps some item picked up in the shop but missed by Rannos Davl, or maybe new horses are stocked and one happens to have horseshoes made by a certain smith and used exclusively by some trading house from Dyvers, Greyhawk, Narwell, or what-have-you. This could prove that the Traders are in cahoots with the raiders and lead the characters off track and onto the roads. Astute players might even disguise themselves as a small trade caravan to act as bait along the High Road. Such a tactic is too dangerous for 1st level characters but might work better for 2nd to 3rd level characters.
Where is all that loot going to? How does one get to the Temple from the High Road? I assume that there is some secondary road linking the Temple to the High Road in some way, since rumors place Dyvers as the source of the evil and it came along the roads from the east. The Temple maps also show a road along the southern portion of the old fortress, but having it THAT close seems a bit presumptuous. Assuming that the Temple is the only destination for all the loot, the bodies of the slain might be turned to undead creatures and those who survive are taken with the raiders to be sacrificed at the Temple or eaten by the more monstrous inhabitants. I always envision the evil temple in the movie Beastmaster when I think about how this should function. How do the raiders conceal their tracks? They are moving to and from marshy terrain which should hold some tracks fairly well, even if it washes away scent. A ranger should be able to follow the tracks of the raiders from the High Road and track back to the moathouse (assuming someone rolls a ranger in the party). Elmo could lead the party as a guide (or hire out as a guide) and track the raiders. Perhaps that is why Gygax placed a ranger as an accessible party henchman... The extra mileage through forested hills and marshland could spawn more wilderness encounters or perhaps another band of brigands working the road closer to the Temple.
It always bugs me that the higher-level NPCs in communities never get involved in the defense of their homes. They always seem to rely on strangers to fix their problems. In this case, however, Elmo would be a perfect candidate to help a fledgling party not only locate the source of the problem, but fight alongside them as well as a super-competent fighter, perhaps defending the weaker members of the party from certain death. He would be a boon to have against the ogre and other humanoids in the moathouse for certain, being able to cause massive amounts of damage with his axe (9-16 damage to the ogre per swing!). In addition, once he has fought with the party, Elmo could vouch for them with the other community leaders. I see Jaroo and Gundigoot being the most involved here, with Rufus perhaps the next most interested. Burne might keep tabs on the party through Rufus, although Rufus would most definitely NOT go adventuring (as stated in the module). Since Elmo is also one of the Viscount's men, he might report directly to the Mayor and the Captain of the Guard, thus informing them of the party's intentions, motives, and valor in combat.
Okay. So now I have more information to create additional scenarios. I can set up a raid encounter with men and/or humanoids from the moathouse along the High Road, or develop random wilderness encounters along the abandoned trail leading from the village to the moathouse since it takes double time to clear the path initially (2 hours walking x 2 = 4 hours to cross 3 miles of overgrown track in a marsh). There must be some wild, dangerous creatures that live in the marsh grass and reeds other than frogs.
No matter how cautious the Traders and the spies are, once they are suspected of wrongdoing they can be trailed and watched by patient characters willing to spend some time gathering intelligence on the situation. Couple this with NPC interactions at the inn or with the villagers and the module starts to expand all by itself. Black Jay the herdsman may be having trouble with sheep missing (taken by raiders to supplement their diet). Farmers might be missing in the community or dogs killed (gnolls might be using them for target practice in the early morning or later evening hours). Of course, there is another angle a DM might use - the characters (if unsavory looking or underhanded) might be approached for recruitment in the Temple forces! They might be asked to spy on someone in the town or report anything the rest of the party learned. They might work through an intermediary (like Zert) until they are deemed trustworthy enough to be approached by a leader (one of the Traders, Lareth himself, or maybe a Temple priest). Such a meeting is not likely to happen in Hommlet, but might occur in Nulb. And this is how the party moves along the adventure path towards the Temple. Remember that the Temple agents are not all aware of each other in the village, and charm spells or high Charisma could work in the party's favor to gain info and earn trust.
Even if the party defeats Lareth and his men, there is little to link them directly to the Temple of Elemental Evil unless the party converses with him. The insignia of the burning golden eye would have no significance to the party unless it had been mentioned previously, or Elmo is with the party. Talking with the other NPCs in Hommlet would also confirm the link between the Temple and the moathouse, especially the Village Elder. Since Terjon is a recent newcomer, he would not likely be aware of the significance of the golden eye aflame. Some instance of this heraldry needs to be prominently displayed or explained prior to the party's approach to the moathouse or the significance will be lost on them. Sages are out of reach of the characters at this level, since they would be unable to afford the fees.