Have you traveled all the way to the back of that cave? There is a thaumaturg’s bench with a tome on it. If you access that, you are going to gain basic knowledge in sorcery.
You know that you have found the right spot when it says (while searching the shaleback cave) “Kurak’s Cave”. Beware, though, that you have to get past all the shalebacks in there, and since they are tough opponents, you’d better run for it. Fortunately they won’t be able to follow you to the workbench.