Epic Levels Question

[Tyrant]

I was looking over the Epic Handbook and a few questions came to mind. I'm fairly new at playing (and DMing) 3.5. The current game might eventually get to epic levels, and I am just curious. The main thing I seem to be not understanding has to do with multiclass characters and those that took Prestige Classes. What all happens when they revert to their base class (as far as taking new levels) and their character level is over 20 but their level in that class is less than 20?

For instance, if someone is a Wiz 10/Red Wizard 10 and then at level 21 they start taking Wizard levels again what do they follow from the Wizard progression and what do they follow for Epic Character rules?

Or what about a Psion? What if someone has a Psion 5/Wiz 5/Cerebremancer 10 and takes a 6th level of Psion as their 21st level? The Epic Psion listing says they don't get any more power points after level 20, but is that only if their 20 levels are all Psion levels or in the case I mentioned would that not kick in until they took 5 more levels of Psion (giving them 10 levels of Psion and 10 of Cerebremancer giving them effectively 20 levels of power point advancement)?

[Jormengand]

You keep following the normal rules for the class (except that base attack and saves no longer advance) until you hit 20th level in that specific class, and then you take the epic levels. For example, a wizard 10/red wizard 10/wizard 5 gets a single wizard bonus feat and five caster levels for the extra 5 wizard levels. When you take wizard 10/red wizard 10/wizard 11, then you'll start taking the epic wizard progression. All the epic progression tells you is what the 21st and beyond levels of the class look like.

[DarkSoul]

You follow the class progressions for all your classes until you hit their maximum class levels, regardless of what this puts your character level at. The exceptions are base attack bonus and base save progressions, which follow the chart on page 6 of the Epic Level Handbook. At odd character levels you get a stacking +1 epic bonus to hit and even character levels give you a stacking +1 epic bonus to all your saving throws.

For caster classes (including psionic classes), you follow the chart for your class until you reach the maximum caster level and have all the benefits listed. After that you don't gain any more spell or power access. The Red Wizard example already has 20th level wizard casting because Red Wizard is a full caster progression class (giving you an additional caster level and spells per day at each class level), so the only thing a Wiz 10/Red Wizard 10 gains from taking 11th level Wizard is an additional caster level and +1 to hit.

Your Psion/Wizard/Cerebremancer is 15th caster/manifester level so taking another level of psion will increase their power points and power access, just as though they'd been a psion 15 leveling up to psion 16. Again, because they're character level 21 they don't get BAB or saving throw increases, they get the +1 epic bonus to hit instead. Once you hit 20th caster or manifester level, such by taking 5 levels of psion or wizard, then you don't advance further for that casting type.

[Khedrac]

For instance, if someone is a Wiz 10/Red Wizard 10 and then at level 21 they start taking Wizard levels again what do they follow from the Wizard progression and what do they follow for Epic Character rules?Note: the rules are also clear that 10-level prestige classes should have their own epic progression to be developed according to the examples given (so DM and player co-operate normally).
This does not apply to 9 or fewer level prestige classes.

Thus the Wizard 10/Red Wizard 10 usually goes to Wiz10/Red Wiz 11 at level 21.
The Wiz 10, Abjurrant Champion 5, Archmage 5 suddenly realises that now the campaign has gone epic his build will rapidly become less useful and probably goes either Wiz 11 or Fatespinner 1...