A hermit is basically a wizard that practices magic at the cost of secluding life from others, meaning that the hermit obviously wanders around the realm trying to research some new magic stuff. If your character do stumble on the hermit, there are few actions you can possibly do with that weirdo:-
(a) Pay the hermit 50 gold to rid yourself of any negative stats( namely disease, curse, frogged etc.)
(b) Give some food to the hermit. A good Samaritan always get something good if the hermit appreciate some yummy stuff (preferably meals or apples). Chance to gain 1xp.
(c) Rob the foolish hermit, this crime really pays off, a chance to explore his inventory. But sometimes he slipped away (damn hermit) and you might get recognized by the authorities. Only rob him if you are a rogue.
(d) Capture the hermit. You can sell him as a slave and during Inqusition (when magic is outlawed and wizards are criminals) the hermit pays for a good sum of gold. If you are a Viking, this action gives you +5 and a rope in your inventory gives an additional +5.