Referred to as Scumcast by most gnolls when they are sure he isn't around, this is the gnoll wizard who'd been casting Wish. He's taken up residence in an observatory on the southern edge of the Crest Mountains.
It's time for the resistance to send a party to take care of him before he wreaks more havok. Better to face him alone than in the middle of a battle where he's not expected.
You talk to Xander who has been to the observatory many times. He tells you about its three levels. The top floor houses the telescope. The main floor is a work area and a bedroom. The basement is for storage and where novice spellcasters would stay. Most likely there are multiple ways to get inside.
After teleporting to The Avium the party began their trek to the observatory. A couple days in Amachai spotted a gnoll flying steed heading toward the observatory. He pointed it out to Dúne who drew his bow (cast Haste) and shot down the pterodactyl-like creature. For good measure he put a couple arrows into the gnoll as it fell too. They hiked over to the body and found a message from General Groundfang to Fang the Damned. It appeared Fang was going to attempt something his brother (that was new information!) didn't want him to do. That night, Dúne sensed a portal of immense size in the direction of the observatory.
A couple nights later the party came upon on of the cabins that had been used, back before the gnolls arrived, by students of the Avium to get to the observatory. This one was occupied by some gnolls, with an inattentive guard outside. It was a quick combat where the gnolls tried to throw a box off the nearby cliff to keep the party from getting it. Two gnolls survived, one wasn't terribly cooperative which cut the count down to one who, after answering some questions, was killed and turned into a zombie by amachai and given the title General Commander Rob the Zombie. Some jokes were made about their old title, the Butchers of Meadowfen.
Amachai performed a ritual and asked his god Tyton how to destroy the phylactery. The answer came back, "Throw it between the worlds and he will never come back."
The box was supposed to be delivered to General Groundfang along with the message from Fang, My life is in your hands. An identify spell, knock, and another identify spell, and the party realized that inside the box was the phylactery of Fang, who'd turned himself into a lich, sacrificing Tare-gat. This was disappointing to learn that Tare-gat had been alive and now they wouldn't get to kill him. And also, they would soon be facing a lich.
The next evening they reached the observatory. Searching the outside they found a series of pipes going into the cliffside. Cyrus tapped into one and a blue-ish liquid covered him, causing quite a bit of damage. (Also, he gained proficiency in a random saving throw, but that's meta-gaming and takes us out of the narrative.) Moving on, the party found a pool of water with a drain pipe that went into the basement. Skipping the actual observatory levels, they began exploring.
The first level of the basement appeared to be living quarters for students, or more recently, gnolls that had trashed the place. A more thorough examination revealed a secret trap door, which dropped down into a different level of the dungeon, an oubliette of sorts, although this reference was completely lost on the party who only wanted to get to the lich, not expand their vocabulary.
Dropping down to the next level, the party discovered a pit trap, with a teleportation rune at the bottom that sent the victims to a room above the trap. When the lever at the bottom was pulled it released the victims and they fell into the trap a second time. Well, that's how it was supposed to work but Cyrus the Monk was the one who fell into the trap so it wasn't as cool as the DM hoped, what with slow fall and everything. The party did appreciate the attempt.
There was a nice ring (Ring of Swarms) the party found at the bottom of a foul pool of water. And some nice poison that Cyrus took. And some skeletons that exploded in necromantic energy when killed. That was fun. Also, more pipes like they'd seen outside.
About this time Dúne was almost incapacitated as he sensed the portal from a few nights ago open up again. This time directly below them. While he wasn't sure of the size, it was the immense power of it that felt overwhelming.
The next level down they found a whole pool of the magical liquid Cyrus cleverly discovered on the surface. A few arcana checks later and (one down one zombie they had jump in) they were pretty sure this was some form of pure magic. Most likely this was connected to the portal.
Further back in the underground structure they discovered an altar with Tare-Gat's body on it. He'd been ritually killed, which fit in with what the party knew about lichs. Cyrus set about destroying the altar and it shifted. Snow helped push it and they found a staircase leading down.
On the way down (to the last level) Fang began speaking to them. He told Snow he knew where Evelyn was and showed an image Snow's mind of her chained to the floor in front of a gate with brainlike creatures coming through toward her. He revealed to Amachai where Conicus was being held captive, in a giant temple dedicated to Anubis. Dúne was shown his sister Madricen serving Tisk, saying Dúne could rescue her. Dúne knew she was safe though, having rescued her and Tisk recently. Adina was offered the knowledge, hey, wait, where the hell's Adina? It's like she totally blew off the second half of the mission because she was there for the first half last week and said she'd make it for the second half. Anyway, Cyrus was told they all have the same goal-destroy the mind flayers. And Fang had a plan that would do just that if they would let him proceed. Otherwise, Evelyn, Conicus and Madricen would all be killed.
They arrived on the bottom level, a huge inter-dimensional gate was on the floor but only showing stars and flashing colors. The party plied Fang with a few more questions, but it became obvious that he did have a plan to get rid of the mind flayers, and send the gnolls to a different world. The catch was that he'd also send all of Humblewood with the mind flayers to this "demi-plane". Not an optimal plan if you're hoping to save Humblewood.
A battle ensued with Fang throwing up several defenses that slowed the party down, making them take precious time to get to him. It was inevitable though, one strong spell caster against four hardened adventurers. Any of who could have killed him once they were within striking distance.
When the killing blow was dealt, Fang grinned, telling the party he'd be back, hunt them down and kill them slowly one by one. Which is why it gave them great satisfaction to direct his attention to his phylactery which was floating in the inbetween nether-world of nowhere. It gave them the satisfaction of a job well done thinking he'd be floating for eternity in place outside of any known realm.
Not to be wasteful, Amachai immediately turned Fang's body into a zombie. They explored the rest of the observatory, befriended a gnoll briefly before they killed him, and found some of Fang's notes. This led them to using the telescope and seeing what had to be a Githzerai Encampment, the Temple of Anubis where Conicus was, and Fang's best guess as to where the mind flayers would arrive: on top of Mokkden Caverns.