Three full quest areas full of monsters is going to be a real pain in the ass to get through. I am expecting it would take an hour and a half with an expert group that is well geared, well experienced, and going a power gaming route. But for many players it would take well up to three hours.
I am suggesting:
- Trim down the area
- Limit the options. It is sweet to have the extra quest area and the big giant back story to the castle, but in the long run it is not going to have that much benefit to players. People are already going on a long quest and it would take even longer to do the extra mercenary side-quest. I do love the idea of being paid off or offing the lord, lady, and steward.
- Keep the statues/portraits depicting former rulers
In the end, this is an ilithid brain trap so perhaps the quest could start off with finding a strange pool of liquid and drinking from it, or finding the ilithid's lair and being caught in a trap. That way through out the quest you can see the ilithid from time to time laughing or doing cruel things to you.