From the WotC plot recap:
"Heroes of Loudwater, flock to my banner and let us do a good thing for the entire Delimbiyr. Too long has the Hark and his brood tormented the tradeways between Loudwater and the Sword Coast. Too long has it infected its plague to others. And now there is evidence that it wants to expand its territory into our very city. It is the duty to all good people to diminish this foe. I go. Who goes with me?"
- - Stedd Rein
- - 13th of Eleint
- - Year of Wild Magic
With these words Stedd Rein, the leader of the Red Fellowship, sent a call for all those noble and brave to join him to attack the dreaded Hark in his own stronghold – the infamous Dungeon of the Hark. High Lord Kalahar Twohands did not directly support Stedd's assault on the Hark, but did not move to block it either. When the Order of the Jade Blade agreed to join Stedd and take the battle to the villain, Kalahar gave his tactic approval.
For those of you who are not familiar with this scourge upon the Delimbiyr Vale, the Hark is a legendary wererat bandit lord who is said to lair in a series of caves and pits under the High Moor called the Dungeon of the Hark. He has haunted our lands for hundreds of years, disappearing for a while and returning to raid anew. To my knowledge lycanthropy does not give a person longevity, so I suspect that the Hark is either a series of separate individuals claiming to be the Hark, is undead, has dragon's blood, or is a fiend of some sort. There are many other possibilities as well. Currently, the Hark favors goblins, hobgoblins, and bugbears as his minions, some of whom have been affected with lycanthropy. The Hark and his band pose a threat to Loudwater and removing him would make the Delimbiyr safer.
Stedd gathered his forces at the old village of Moorsedge, which sits at the border of the High Moor where the land slopes away down into the Delimbiyr Vale. It is nothing but a ruin now, as the Hark's forces have decimated it when they claimed the dark places beneath to build the Dungeon of the Hark. Stedd sent the Jade Blade to the Worg Warrens which would prevent the wolves from reinforcing the Hark, while Stedd and his Red Fellowship attacked him directly in the main part of the dungeon.
The Jade Blade found the entrance to the warrens guarded by goblins and a large tree with ropes hanging from the branches. They engaged the goblins and quickly learned that the tree was alive or enchanted, because it attacked them and attempted to strangle them with the nooses. After the initial surprise, the adventurers cut the sentries down and descended into the warrens where they encountered a drunken bugbear and a rat swarm which were both quickly dispatched. Beyond that, they surprised a nasty little goblin named Snig the Axe who led a bugbear and a group of goblins.
The next chamber contained something unexpected – a group of Zhentarim led by a Banite priest. Neither side wasted much time with diplomacy, and after a short and vicious battle, the Black Network operatives were dead. Among their possessions the Jade Blade found a note addressed to the Hark from Felishar Ivasin, the mayor of Orlbar and a member of the Zhentarim. Felishar was conspiring with the Hark against Loudwater and the Zhentarim that our heroes slew were in the dungeon as ambassadors. The note hinted that there was a "young red dragon" in the Greycloak Mountains that would soon be within the Zhentarim's grasp. The note also made mention that the Hark was from a place called Fury's Heart, which is a different plane and the home of Malar among other evil gods.
The Jade Blade pressed deeper into the dungeon and came across a wererat who was bowing before a large brazier. In the smoke of the brazier was the image of a dark-red-skinned goblin with glowing green eyes who was telling the bowing wererat to prepare the worgs and that he is going to trick Stedd Rein into a tunnel that leads to a mind flayer warren while he took a different path out through the Worg Warrens. The Hark was coming this way!
The bowing wererat noticed the adventurers and fled into the next chamber to warn Uzetuk, a hobgoblin cleric of Malar and the Master of the Worg Riders. Uzetuk led a counter-strike against the adventurers that consisted of him, the wererat, a couple goblins, and some disturbing aberration that was humanoid in form but had a single enormous eye dominating its face. The Jade Blade managed to defeat Uzetuk and his minions, but it cost them dearly in their supplies and health. Attrition was starting to take its toll.
In a nearby cave, our heroes discovered the worgs which the Hark was planning on using for his escape. They slew the beasts but triggered a trap that caused wolf skeletons to rise and attack them. The undead weren't difficult, but it was more time and energy spent, and the Jade Blade had little of either left. After this battle, the adventures met the final defenders of the Hark: a hobgoblin, more goblins, and a bugbear. The battle went poorly for the goblins, so one of them opened a door to let in a pack of abyssal maws which savagely attacked the adventurers. Maws are some sort of horrific creature from another plane, and they seem to be half teeth and half appetite. The things chewed into our heroes and nearly swung the battle back in favor of the Hark's defenders.
The battle ended and the Jade Blade was victorious, but only barely. They were spent. Their healing powers were used, and their magic was drained. They were all wounded, and had nothing left to open the final door and possibly face the Hark himself. They decided that pressing on would lead to nothing but their death. The Jade Blade retreated from the dungeon without seeing the Hark.
Do not think that they failed. Oh no. The Jade Blade destroyed a large part of the Hark's defenses and slowed his escape. Stedd Rein wisely avoided the tunnel that lead to the Underdark and the illithids. The raid was a success. The wererat's power was broken and his stronghold cleansed. The River Shining would flow past lands that did not fear the terror of the Hark.