I was wondering what exactly do the mage spells "Lesser Dispel", "Dispel Magic", "Greater Dispel", well, dispel? I tried casting them on enemy mages with protection spells, doesn't seem to do anything. I tried casting them on my allies suffering from ability and/or level decrease, doesn't seem to do anything either.

Also, what is the difference between the shadow version (from spells such as "Shadow Conjuration") of a spell and its actual version?

Any help is greatly appreciated!