Focus Skill

Focus is, broadly speaking, how fast your Hit Points and Stamina regenerate. You will notice how important this skill is early in the game. Especially while your stats are still poor and untrained, you will find yourself unable to walk with no stamina left. Your Stamina regenerates in proportion to this skill.

Divine Fury (Divinum Furis), a Paladin spell, refills Stamina, and Refresh Potions do pretty much the same job. For that reason you may prefer to pick other skills instead of this one.