Nexus Tower-Shaft to the Sanctum

[Tealor Arantheal]

Actually you should be able to complete the quest.

If you killed that star scientist there should be a note on his desk.
This note advance your quest to the final stage and complete it regardless which stage you currently at.

[Priamo]

I arrived to the "Shaft to the Sanctum" level, until a square room with a big hole in the middle (killed everyone with sneaking and a high level marksman, no idea if there were bosses or not xD). There was a book i opened, but the mission didn't finished.

I have found several problems in some missions caused by installing an unofficial translation to spanish language. I don't know if in this case that was also the problem, probably it was, but today in other mission I had to finally quit the translation to continue playing. If someone reading me has the spanish translation I would recommend removing it to avoid any possible problems in the game xD