The Shriekers can't spot invisible people (so you can walk straight past them with Chameleon Cloak and engage final battle at level 2 if you want). Similarly you can hide from the Void Salamanders, the Deep-dweller, the Source dogs and almost everyone else with this starting skill.
The only NPCs I can find who can see through Invisibility are the Trompdoy clones can see through your invisibility and snap you out of it to say "Wasn't I clear your not WELCOME here".
You can still go invisible and run away to bypass them if you have enough initiative for them not to kill you first though.
Another odd AI issue is Bishop Alexander and Radaka take an extremely long time to decide what to do compared to other NPCs. Like 5 times as long at least.
After thinking about it for ages if they can't see anyone to attack all they do (every time) is Encourage and then Circle Fence - destroying their own and allies magical Armor and then eventually stunning themselves. Alexander does this both when fighting Dallis and at the end battle. In both cases they'd be better off considering restoration so you can only win if your attack is better than their restoration.
