Adventure Material: Re-Return to the Keep on the Plaplands

I'm currently running a game at the RPG.net forums for the Questers of the Middle Realms rpg. It's loosely based on the (extremely) old school D+D module "The Keep on the Borderlands". It's not a direct adaptation of the original module but it's intended to take the idea of "isolated fortress as the base for a sandbox-style game" and adapt it to the tongue-in-cheek attitude of the Questers setting. I figured, since there's not a lot of adventures out there for PDQ, I'd post the adventure material here as it gets created (needless to say, if anyone from my game stumbles across this, please do not read). 

This is the initial premise for the adventure, posted in the recruitment thread: 

The Plains of Plap is one of the strangest and most mysterious places in Ludor: a large expanse of mostly empty grassland where things and sometimes creatures fall from the sky at random intervals. For the most part it's harmless (if annoying) but occasionally something dangerous lands here and survives to make trouble or someone comes across some unstable magic object and blows up an inn. Thus it was decided to build the Border Keep on edge of the plains, placed along a pass through the hills that surround Plap. The keep serves to keep watch should anything deadly try and make its way out of the plains and also as a trading post where scavengers can sell interesting things that have fallen from the sky.

After changing hands quite a few times no one is sure exactly which nation owns the Keep anymore and no one is willing to send their own troops to keep it manned. Thus the armed forces of the keep mostly consist of a few locals and questers who come by looking for work. You've been here once before...but it was boring and you left. Then you came back...but someone had to get drunk and cause a fuss and get everyone else kicked out. Now you're low on cash and you're back...again...hopefully things will go better this time. 

And here's a map of the region around the Keep. This map is a player handout so it doesn't include secret or unknown things (such as the main dungeon, the Caverns of Whatever). 

Part of the original adventure was a random table of different rumors that players might have heard about the Keep and of course I adapted that as well.

Rumor Table (1d20)

1. The frogmen in the marsh often kidnap travelers for cooking (sort of true).
2. Beneath a giant tree lives a hermit, a powerful wizard. (false)
3. Beneath a giant tree lives a crazed old man and his pet giant cat.
4. There is a cache of valuable objects hidden in the Accursed Heap (false).
5. A tribe of beastmen have moved into the plains recently.
6. The really big skull can speak if you address it just after sunset (false).
7. Recently an unknown idol fell from the sky.
8. Valuable objects tend to fall more commonly in the Thicket. (false)
9. A huge giant wanders the plains. No one knows exactly where they came from.
10. There were some particularly large impacts in the last couple of weeks.
11. There's been a sudden influx of dangerous humaniods in the past week or two.
12. One of the scavengers witnessed a dragon fly across the plains (false).
13. There's a series of caverns running under the plains.
14. There's an evil cult hiding among the inhabitants of the Keep. (false)
15. The local jeweler will offer small gemstones in exchange for books
16. Travelers in the plains have recently seen one of Arrganarr's Night Riders
17. There's a underground tribe of kobolds in the hills near the Keep.
18. One of the most dangerous threats on the plain are herds of Dread Sheep.
19. A talking suit of armor can be found at the Accursed Heap (false)
20. A band of thieves stays in the Keep, fencing dangerous and illegal goods from the plains (false)