H2 - Thunderspire Labyrinth
This adventure takes place in the Seven Pillared Hall, an ancient city once the hub of a minotaur kingdom and other dungeon areas in the tunnels under Thunderspire Mountain in the Nentir Vale.
Paldemar a wizard follower of Vecna seeks to take control of the Seven Pillared Hall. In addition slave trading hobgoblins (the Bloodreavers) and duergar (the Grimmerzhul duergar) have kidnapped townsfolk from the surface town of Riverdown, and demon woshiping gnolls (the Blackfang gnolls) have their own agendas while all working with Paldemar on the side.
The Bloodreaver hobgoblins, whose chief Krand is connected to Kalarel from H1 - Keep on the Shadowfell provide two of the plot hooks to kick the adventure off. Lord Padraig of Winterhaven may ask the characters to eliminate the threat that they pose to the Nentir Vale, or the people of the surface town of Riverdown may seek the characters help in rescuing captive villagers. The final plot hooks are to courier goods to a drow fence named Gendar, and to investigate the minotaur ruins found within Thunderspire mountain.
The adventure begins with the characters entering the tunnels under Thunderspire Mountain, and stumbling across Bloodreaver gang hobgoblins menacing a halfling Rendil, whos family runs a tavern, the Halfmoon Inn, in the Seven Pillared Hall.
The Labyrinth of tunnels and chambers bored into Thunderspire Mountain is a notable "character" of this adventure. It is expected that travel from location to location will result in the characters occasionally becomming lost, encountering random monsters in the depths of the mountains, and otherwise interacting with the maze of tunnels.
The Seven Pillared Hall acts as the characters home base while exploring Thunderspire. The hall is a large cavern supporting a small trading town, in which denizens from the underdark and merchants from the surface world can meet on neutral ground. Peace in the hall is kept by the Mages of Saruun, of whom the characters will meet Orontor who will tell them of the missing Paldemar, though Orontor does not know of Paldemar's plot. When this meeting happens is unspecified, thought he module suggests that Orontor be met earlier than later.
Rendil provides the characters with directions to the Chamber of Eyes a dungeon location near the Seven Pillared Hall that was once a temple to Torog, but is now the home base of the Bloodreavers and their chief, Krand. During this segment of the adventure the players encounter some duergar who are completing their side of the sale of the Riverdown captives who have now been transported to the duergar fastness, the Horned Hold, though they do not learn the name or location of the hold.
Up next for the characters is to return to the Seven Pilared Hall, determining what to do next if they are not sure, and then learning where to find the Grimmerzhul duergar who have purchased the Riverdown captives. The duergar have a trading post in the Seven Pilared Hall and the characters can find the Horned Hold by interrogating one of the duergar, by ransaking or searching the trading post, or by buying the info from Gednar (the drow to whom one of the opening adventure hooks points).
So eventually the characters make their way to the Horned Hold where they fight their way through the dueargar, and the allies, defeating the duergar leader Murkelmor, a paladin of Asmodeus and rescure the townsfolk. The most notable aspect of the Horned Hold itself is that it is built straddling a great gorge, with bridges spanning the gap from the two southern keeps (from where the characters approach) to the northern keep (where Murkelmor and the captives are to be found).
The characters learn from the captives that two of their number were sold on to some gnolls. The successes the players have had in dealing with the Bloodreavers and the duergar cause Paldemar to strike at the characters before they damage his plans further, and so dispatches a team to ambush them. The ambushers helpfully bring along letters implicating Paldemar, naming a tribe of gnolls, the Blackfangs, and their chieftan, Maldrick Scarmaker, as his allies, as well as providing a map to the Well of Demons where the gnolls lair.
The Well of Demons is a former temple of Baphomet which the gnolls are intending to redidicate to Yeenoghu. In addition to the gnolls, the Well of Demons contains a series of tests that the characters must pass if they are to enter the inner sanctum where they do battle with Maldrick Scarmaker, rescue the final two captives, win an item called the silver key which both unlocks Paldemar's lair (a place called the Tower of Mysteries) and gives a vision of how to get there, and learn for sure, that Maldrick Scarmarker and Paldemar are in cahoots.
The tests the charactes must attempt, and the rewards they receive for doing so are: the Hall of Enforced Introspection in which they win the Face of Baphomet, the Hall of the Crimson Whip in which they win the blade and the hilt of the Bloodhorn Blade, the Hall of the Howling Pillars in which they win the Bell of Fury's Calling, the Proving Grouds in which they gain access to the inner sanctum.
The characters have now uncovered Paldemar's plans, and so proceed to Paldemar's lair in Tower of Mysteries to confront him.