As player characters overcome challenges, they gain experience points. As these points accumulate, PCs advance in level and power. A character advances in level as soon as he earns enough experience points to do so—typically, this occurs at the end of a game session, when your GM hands out that session’s experience point awards.
The process of advancing a character works in much the same way as generating a character, except that your ability scores, race, and previous choices concerning class, skills, and feats cannot be changed. Adding a level generally gives you new abilities, additional skill points to spend, more hit points, and possibly an ability score increase or additional feat.
When adding new levels of an existing class or adding levels of a new class, make sure to take the following steps in order. First, select the two classes to advance; these may be classes that you already have (in which case your current class level increases) or may be new classes (in which case you obtain the 1st level benefits that class). You must be able to qualify for this level before any of the following adjustments are made. Second, apply any ability score increases due to gaining a level. Third, integrate all of the level’s class abilities from both classes; as always, if the same class feature is gained from both classes that feature accrues at the rate of the faster class. Then, roll for additional hit points using the larger of the two hit dice. Finally, add new skills and feats.
At any given level only one prestige class may be taken at a time. In addition, you can only take up to 20 levels in a core class, and up to 10 levels in a prestige class (assuming, of course, that 10 levels are available to take). Although hit dice, base attack bonus, saving throw bonuses, and potentially caster level will accrue normally, there are some limits. There are no spell slots higher than 9th level. As always, spell slots granted by high ability scores may be used to hold spells of lower level.
At 18th level you can choose a destiny for your character. The destiny represents your character’s path to immortality — his or her final place in the universe.
Your destiny describes the mythic archetype you aspire to achieve. Some characters have a clear destiny in mind from the moment they began adventuring, while others discover their destiny somewhere along the way. Most people don’t ever come close to achieving an destiny. Whether they simply failed in their journey, or whether the universe never intended them to gain such lofty heights, is unknown and unknowable. Your destiny sets you apart from such individuals —- you know you’re destined for greatness and you have every opportunity to achieve it. Your destiny defines your lasting impact on the world or even the universe: how people forever afterward remember and talk about you. Some people may achieve great fame or notoriety without achieving a destiny, but that’s a fleeting thing. Inevitably, those people are forgotten, lost in the murky depths of history. Your destiny ensures that your name and exploits live on forever.