First, shoot the spear gun through this window.
Next, go over by this part of the level.
Turn around, use the scrye and you'll see this portal. Jump in...
...and there it is...the talking donkey!
Damn donkey should have said something better.
When you get into the room with the talking donkey, turn left and use the dispel spell on the wall in front of you, walk into it and it will open and in there you'll find a note from one of the makers to his wife.