Following their trouncing by the drow elves in the eastern passages of level 3, the party stealthily retreated to the west and south after sufficient recovery (in 5E terms, they finished a long rest). There was a straightforward battle with a chimera in a side cavern, and then the party scouted a ruined dwarven city sprawled across the floor of a very large cavern. The ruins were inhabited by giant spiders and drow patrols. They took refuge in an abandoned dwarven dwelling and surprised a lone drow elf while he was relieving himself. He was quickly taken prisoner.
It's been a long time so I don't remember exactly the word they used to intimidate or cajole the lone sentry to guide them through the ruins, avoiding watchposts and getting past the drow garrison in the ruined city. But they left the low level drow flunky once they got beyond the city and made their way through warren-like tunnels to the edge of hobgoblin territory. Again there was more negotiation, this time convincing the hobgoblin captain in charge that they were also enemies of the drow and potential allies to the hobgoblin nation. (By way of reminder, the player's objective on level 3 was to find their way to the underground pirate city of Skullport and they were hoping to get the location from the hobgoblins).
The Legion of Azrok is the name of the hobgoblin kingdom on level 3 of Undermountain. I'm not familiar with the original Undermountain, but there were elements of Azrok that reminded me of the old Orcs of Thar Gazetteer from Mystara era Basic D&D. Humanoid societies there were presented as mirrors of the human world; the hobgoblin stronghold, with its building sized banners festooned with the Legion's heraldry gave it the feel of an autocratic police state; militaristic hobgoblins patrolled with regularity, checking the "papers" of visitors like the KGB or gestapo. The players were subjected to the surreal experience of being marched by uniformed hobgoblins to a chamber where bespectacled goblin artists hastily sketched "guest visas" for visitors to the hobgoblin nation. It was good for some comedy.
It turns out the hobgoblin nation was in dire straits. The drow elves had recently invaded from a lower level, driving the hobgoblins out of the eastern part of the ruined dwarven city and inflicting heavy casualties. The Legion of Azrok was on a war-time footing. They were casting about for allies. An ambassador from Xanathar's Guild was being entertained, a mind flayer named Ulquess. The pirate city of Skullport sat nearby to the west of Undermountain level 3, and apparently Xanathar now controlled the entire city. The hobgoblins were open to an alliance with the beholder Xanathar.
In their audience with the hobgoblin king and his queen, Lurkana, the players offered to help the hobgoblins against the drow, in return for safe passage to Skullport. However, they wanted a private audience with either the king or queen. The news that a mind flayer ambassador was loose somewhere in the Hold of Azrok was chilling to them. (Whether you're new to these game reports or not, there's been a campaign-long theme where mind flayers allied with Xanathar's guild are using intellect devourers to murder and replace prominent people topside in Waterdeep City). The players were immediately concerned the hobgoblin court was compromised.
The characters had a small supply of Potions of Mind Reading in their inventory, going all the way back to when they were adventuring topside in Waterdeep during the Dragon Heist phase of the campaign (they got roped into a Zhentarim side mission that involved knocking over a potion shop). Ace, their elven wizard, now used one of the potions during their private audience with Lurkana to verify neither she nor her guards secretly had mind flayer pets lurking in their skulls.
The players convinced the queen to let them stage a dramatic scene in front of the hobgoblin court where one of the characters gave a fiery speech about the dangers of an alliance with Xanathar while Ace used a second potion to scan the thoughts of the assembled courtiers, a mix of hobgoblins, goblins, and bugbears. One of the bugbears was being controlled by an intellect devourer and made a break for it when Ace touched its mind. There was a short duel, the assembled court saw the bugbear's empty cranium and the horror of the emerging intellect devourer, and orders were issued to have Ulquess, the Xanathar ambassador, arrested.
The players decided a patrol of hobgoblins was no match for a mind flayer. "I've sent a patrol of my best soldiers, they're already bringing the ambassador back here" said the queen. "No", said one of the players, "Your men are already dead". So they went themselves to the ambassador's quarters. They were ambushed by a fair number of denizens who had already been replaced by mind-controlled servitors. The mind flayer had been busy preparing defenses around the embassy, and had defensive contingency plans in place.
When the dust settled, the mind flayer was long gone - probably levitating to the top of the cavern once it learned that its network of spies was compromised. The players had to slaughter a half dozen intellect devourers and their mind-controlled goon bodies. The threat ended, the hobgoblin court was grateful and the players were elevated from guest visas to permanent residents if they wished.
Over the next few days, the players learned more about the hobgoblin nation and the politics of level 3. Interesting encounters included a demonic hobgoblin trader, and a mutated necromancer, exiled from the depths of Undermountain. The necromancer was slowly building a zombie army to help tip the hobgoblins tip the scales against the drow. Her stories and rumors gave the players a glimpse of what’s waiting in the depths of Undermountain.
Ultimately the hobgoblins decided to cease diplomatic relations with Xanathar's Guild and close the passages between Skullport and the Hold of Azrok. A missive was drafted and prepared to be taken by courier to Skullport, to be presented to one of Xanathar's agents. As the players were desperate to go to Skullport, they volunteered to take the diplomatic letter to Skullport themselves. We'll pick up the game reports next time with their first visit to Skullport.