Finished editing.
1) Does Karlane know the name of the man who first came out of the list (that Idrys Backstabbed)? No
2) Does Karlane know the name of the man clad as a mage that has just arrived out of the elevator? No
3) has Karlane heard of Lord Altradeaus ?
4) The leader clearly wasn't expecting Idrys's backstab, so wasn't there a possibility of surprise (DMG p63)? (needed 1)
5) When the leader '...runs frantically toward a pillar...' certainly sounds like fleeing away from Idrys, if so the latter would be allowed an additional full set of attacks, (DMG p70). Avoided said opportunistic attacks for a specific reason
6) What's the visibility distance in the 'thick, obscuring mist'? 3 radius
7) When the leader bursts out of the mist he seems to know exactly where the usually silent Idrys is. While the leader has run off, pressed a button, pulled out a trident and operated it, has Idrys really not moved? Idrys is silent, but not invisible. While moving silently, which takes longer than ordinary walking boss-man is able to position himself since he's not stealthy and just moving ordinarily. He moved behind the second middle of the chamber pillar.

9 ) Leader says 4 sentences, removes teeth and throws them. Sounds like at least another round off Idrys's 5 rounds of being held (and probably 2 rounds, if I'm honest). Tracking it
10) '...Lucien drew Karlene's attention toward himself...' and thereafter Lucien attempts and fails to make (multiple) attack attempts on the leader (during which time the leader '...unfasten[s] his trident...twist[s] one part...into a spear-blade) has got to be two more rounds. This should go off Idrys's 5 rounds of being held, shouldn't it? Idrys str check: 18, he needed a 9 or less to break
11) Doesn't Karlane get any actions between when Lucien drew her attention and when the leader has finished producing the spear blade?
12) The leader stares at Karlane... that's quite a trick through 'thick, obscuring mist' and as she's wearing Cloak and Boots of Elvenkind. Doesn't she get a chance to surprise him? Or to act in some manner, for at least 1 round?
13) After ]staring at Karlane, the leader talks. A lot. 67 words. That's at least 5 segments. Can Karlane act while he talks? Any impact on Idrys's 5 rounds of being held?
14) 'Sarancen and Azonia came up behind the boss...' who '...turned and sneered at the two fighters...' Can Karlane act (being behind him) while he talks?
15) Initially '...The elevator comes to a screeching halt...' but there was no mention of it rising, someone entering, and descending again.