Weirdest thing happen to me yesterday:
During the past two weeks I loaded my stuck Bookworms mission with human mercenaries in which the deamonette was blocking my progress a couple of time just so I can keep throwing nimble Luthor of a cliff to avoid dishonorable and costly abandon mission. In the mean time I played other warbands. So yesterday I load in order to finish the job and finally restart the mission. Just as I got Luthor's health to one last fatal jump, I thought I'd check the blocked portal one last time just for fun. And my leader gets through. Standing right beside the half fdead deamonette.
Turns out that my ogre that was the first to fall to the deamonette, and is the reason she was blocking the portal, was uniquely qualified for that fight due to his stun resistance. My leader land a few blows on her before he gets stunned and succumbs, And she's blocking the portal again. For a few turns.
I reload, once. Twice. And My champion gets through to charge the deamonette. So he moved of the portal and my henchmen start pouring through. The champion is out by the next turn, but now my terror struck warriors surround the deamonette on her last breath. And they start dropping like flies. Stunned. Terrorized. One or two lucky hits later the deamonettes back in the chaos realm, and my men get to book browsing. Btw. the looting bags aren't blocking the portals cause there are three of them on top of it by now and it is functional.
After the deamonette's gone, the horror ensues.
I mean literally, the Pink Horror enters the main room as enemy reinforcements. He rapes my warlock that I've left behind as rearguard. Luckily, I manage to squeeze Luthor who is down to a one digit number of wound points, from doing extreme sports earlier, through the orange portal into the deamonette section where the rest of the warband is. By now, I'm down to a few terrorized henchmen and a marksman. I wait till they all regain their wits to head back to the main hall and face the Horror that did not fallow us through the orange portal. Only to find out that the Horror has planted himself on the exit portal in the main hall and is blocking my return from the deamonette section.
Fortunately, you can leave the deamonette's little penthouse by jumping down to the ledge just above the place where the Bloodletter used to block his portal.
So, I do that, grab the last tome and rejoice.
In the end my advice is, load and reload a few times to see if the deamonette moved off the portal just enough so push someone though.
Turns out this might not be a Gamebreaking glitch / bug after all.