Assuming PHB races only:
Edena_of_Neith said:
One.
Three. One normally, one as their Haste partial action, and one Quickened.
Well, the Cha(27), Cha(30), and Wiz(29) feats shoudl all go to Autoquicken. That leaves four more feats for Multispell, so the answer here is:
Seven. One normally, one hasted, and five quickened.
Note that THEORETIALLY, the Wizard could have taken three mroe Multispell feats instead of the Autoquickens, bringing the total up to 10, but -- that's not min/maxxed. With three autoquickens, EVERY spell up to 9th level is quickened, for free.
Same as 30th level, or maybe, another Multispell here and there. There comes a point where "enough is enough", after all.
However, theoretically, you could have a feat chain like this (ignoring everything below 20th level, as it doesn't change how many spells you can cast):
Wiz20 Quicken Spell
Cha21 Multispell
Wiz23 Multispell
Cha24 Multispell
Wiz26 Multispell
Cha27 Autoquicken (1-3)
Wiz29 Autoquicken(4-6)
Cha30 Autoquicken (7-9)
----------[ 7 spells per round max, all spells level 1-9 quickened for free ]----------
Wiz32 Improved Metamagic (1)
Cha33 Improved Metamagic (2)
Wiz35 Improved Metamagic (3)
Cha36 Multispell
Wiz38 Multispell
Cha39 Multispell
Wiz41 Multispell
Cha42 Multispell
Wiz44 Multispell
Cha45 Multispell
Wiz47 Multispell
Cha48 Multispell
Wiz50 Multispell
----------[ 17 spells per round max; all metamagics cost 3 levels less, all spells level 1-9 quickened for free ]----------
Cha51 Multispell
Wiz53 Multispell
Cha54 Multispell
Wiz56 Multispell
Cha57 Multispell
Wiz59 Multispell
Cha60 Multispell
Wiz62 Multispell
Cha63 Multispell
Wiz65 Multispell
Cha66 Multispell
Wiz68 Multispell
Cha69 Multispell
Wiz71 Multispell
Cha72 Multispell
Wiz74 Multispell
Cha75 Multispell
Wiz77 Multispell
Cha78 Multispell
Wiz80 Multispell
Cha81 Multispell
Wiz83 Multispell
Cha84 Multispell
Wiz86 Multispell
Cha87 Multispell
Wiz89 Multispell
Cha90 Multispell
Wiz92 Multispell
Cha93 Multispell
Wiz95 Multispell
Cha96 Multispell
Wiz98 Multispell
Cha99 Multispell
----------[ 49 spells per round maximum, all metamagics cost 3 levels less, all spells level 1-9 quickened for free ]----------
Mind you, there are far better ways for some of those feats to be spent (say, one Enhanced Spell metamagic per 10 levels; Epic Spellcasting; and a few other good spellcasting epic feats). Those would consume
A Fireball [Enhanced(4), Twin, Maximise] would still be automatically Quickened for thsi monstrousity (since it uses a 9th level slot), and would do 50d6 damage, maximised to 300. Twice.
The problem comes down to this: the wizard only HAS so many spells, so ... after a while, taking mroe Multispell feats makes no sense. Some Increased Capacity feats woudl be better.
So, you CAN make a wizard that can fire off nearly fifty spells in a round. However, if you're min/maxxing, you won't WANT to. Ten per round will do you just fine; Increased Capacity and Epic Spellcasting will do you much more good, after that point.
...
So, for the 100th level Wizard, my answer would have to be: ONE.
It's an epic spell, and utterly destroys everything on an entire plane, other than the caster and his or her equipment.
IOW, the 100th level wizard only NEEDS
one spell. 