So, I have this quset about investigating what has happened to Scabban. I found him in the crypt, but when I return to the magick shoppe, the wizards still asks about Scabban. What more could I do, except killing Scabban which I already have done to?

In another thread I read you have to enter the room where Scabban originally was to get the reward for the quest. This room is in the top of the Asylum, probably two floors above where you found him. (You probably found him in the water. That means he already fell down the hole in his room.) You need to go to his room anyway to find the lever to open the gate in the water: that's the way out.
(You can use the search option for Scabban for more details.)

I did the same thing as you, all you have to do is kill him. Didn't you hear him talk about killing everyone else and making them his slaves? This way you stop him and get your quest completed.

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Apprentice2All

Yeah, well, Scabban is stonedead, I killed him after he told me about his plans. I have been in his room above the water filled room, but I still cant rew no freaking reward!