Mages utilise the gift of magic originally given to the dragons to shape and form reality into a manner they see fit. It is an incredibly powerful skill, but has its limits, and takes immense amounts of study to progress in.
Mages are run as written in the Players Handbook, with the following alterations:
If a mage has had at least 8 hours sleep in the last 24 hours, they can rest at any time to re-memorize spells, which takes 10 minutes per spell level.
Mages can perform the cantrip spell at will, and can always do basic magical effects without need to memorise them. This can include an offensive capacity in the form of a ranged attack that requires a to hit roll, and can do no more than 1d3 points of damage.