Fuck it reposting this on its own too as a response to this:
First off, I don't want to completely bury the other things mentioned, because I do think that a lot of people interested in Essek are often also very interested in the wider culture and history of the Kryn Dynasty itself (I know I am!). For as integral as it is to the larger plot of C2, they really only just scratch the surface of it in the campaign. I'd love for there to be a story of some fashion (EXU, novel, more comics, etc) that digs even more into the Dynasty or has a character very directly affected by these events and its actions, but I think to a degree Matt's intention is often to leave plenty of space for people to come in and tell their own stories in these kind of in-betweens. We already know the short answer versions for Den Duendalos and what happened with Nogvurot, and exploring those in some fashion (my kingdom for a PC that grew up in Nogvurot and ended up being a consecuted Kryn soldier) would be very interesting and fun.
But to break down the Adeen fascination (at least for me):
In Episode 99 "High Seas, High Stakes" : when Jester asks Essek if he'd ever talked to Adeen, he responds "We once knew each other, for a while," and upon her follow up of "does he suck" his answer is "that is a word, yes." His manner is fairly neutral, nonchalant even - so it's entirely possible it could be nothing, but it also isn't at all out of character for Essek to obfuscate in this way. However when Beau asks what it feels like seeing Adeen in his place, Essek squares his shoulders, looks smug, and answers "Honestly? Freeing."
Now of course, he's just gotten clean away with treason, but it's not really a stretch to imagine that there could be a note of self-satisfaction and justification at seeing Adeen in particular taking the fall.
This little interaction to me (and others) signals that the relationship between Essek and Adeen is at a minimum a step above "guy I disliked in passing". There's definitely some kind of significant familiarity implied, and Essek tends to be (or at least is meant to be) much more deliberate in his machinations. Adeen was specifically set up to be his fall guy (Link to transcript of Episode 90, "Bathhouses and Bastions", when Essek tells the M9 of Adeen's capture). Having Modify Memory cast on him is likely what caused him to flee, and Essek likely planted the further evidence of the crystals to lend more credence to his supposed guilt. Him allegedly being part of the Angel of Irons which already had ties to an agent in the Empire (Vence) was a way to make a plausible link between the two for having means and motive for also handing over the Beacons. All of this is planted.
The thing that confused me for a while is when Fjord attempts to question Adeen while disguised as Vence, it's very obvious that his memory has been fucked with. The scene is clearly meant to seed the idea to the Nein that something else is going on here and someone else is responsible for what happened, but from a "logical" perspective, it's a little confusing why Essek would allow them to directly interact with Adeen in the first place if he wanted to be perfectly sure that he could control the narrative of Adeen's guilt. What we could infer, then, is that Essek is arrogant enough and confident enough that any admission of guilt is enough for the Bright Queen, and therefore the chances of the Nein being be able to change his fate is slim, so it doesn't much matter (and he ends up being right). Afterward, he notably doesn't bother to correct the Nein's assumptions because while they at first recognize that Modify Memory is likely cast, they eventually come to the conclusion that Adeen was mind controlled by Obann when he actually wasn't.
When addressing the Bright Queen afterward, Essek does not caveat his accusation and results of his interrogation with the Nein's doubts and instead leaves it up to them to try to intercede, but to basically no effect. The Bright Queen basically goes "well someone's gotta be punished", and Essek doesn't try terribly hard to refute this stance, saying and it would likely be difficult to get much more out of Adeen because "he's in a difficult physical state" (how convenient, Essek), but that "the confession stands. But hopefully mercy can be considered." He's very wishy washy about it, because of course he intends to do no such thing, but it's necessary for appearances, as everyone in the room and the audience, upon their first viewing, has no idea that he's the one behind all of this. Further, while the Bright Queen maybe could have been swayed to not outright executing Adeen if they didn't decide to make him part of the prisoner exchange, that would have taken a lot more advocating from the Nein to get there. Being exchanged to the Empire was probably about as 'merciful' as it was going to get.
Essek was probably always going to need a fall guy, so Adeen's existence as a character rather than a complete random one in passing isn't evidence in and of itself that their connection is significant. That said, although "we once knew each other, for a time" is pretty vague, there's plenty of room for argument that Essek's reasoning for choosing Adeen is more than just convenience, primarily because Adeen probably wouldn't have been a suspect without Essek deliberately making him one. It's possible that they were once the equivalent of bitchy coworkers, but it's also possible that Adeen did something significant enough in their shared past that put himself in Essek's line of fire. If you need to frame someone for Treason and you have the opportunity to pick who that person is, it makes sense that you'd pick someone you have beef with.
Or maybe he just sucked. Alas, we may never know.
But yes - give me more Dynasty anything.