You may leave your chosen profession at any time, and may choose a new one, however you will lose all knowledge of all skills and spells when you leave. Mages are the purest of the spell casting professions. They focus mainly on offensive spells and have the most damaging spells of any of the professions. Higher-level mages can do fantastic things like teleport around the mud or wreck an opponents mind. They also can defend themselves by going invisible or by blinking to avoid hits.
Mages lacks the potential to deal good physical damage with weapons.
Warriors are the masters of weaponry. They have the most potential of all the professions to deal devastating physical damage in a melee. They are masters of swordplay, and can use their weapon to parry or disarm their opponents. Also, they can repair weapons and armor that have been damaged, and they can make weapons more effective by sharpening them. Warriors have the ability to bash their opponents, making them temporarily unable to flee.