Mindreading Laiken will spawn a chest behind the throne, containing his sword, a divine charm, another charm and IIRC something else. You get the dragon stone after killing Laiken, anyway, so if you don't care for the loot you don't need to mindread him.
Barnabus is in a cave near the start of the fjords, which you can only reach after you have the dragon stone. He drops a hammer anyway (which is very nice, and I used it for quite awhile) and another hammer if you mindread the demon; I didn't end up using the demon's hammer, but the 'wasted' experience points didn't hurt any.
