Human Tra5/Red26/Acm5.
Restricted schools: Conjuration (Tra1), Evocation (Tra5/Red1)
(Note that you will still be able to use scrolls and wands that duplicate all 1st-3rd level evocation spells you know, so pick up a few of these.)
Go with the following route:
Initial stats
Str 13
Dex 14
Con 17
Int 18
Wis 15
Cha 18
Stat increases go into Int (levels 4-32) and then Con (36). New stats:
Str 13
Dex 14
Con 18
Int 26
Wis 15
Cha 18
Max Knowledge (arcana), Concentration, and Spellcraft. Pick other skills as desired, since you have lots of skill points.
Feats:
L1: Tattoo Focus, Scribe Scroll, Improved Initiative
L3: Extend Spell
L5: Craft Wondrous Item
L6: Spell Focus (transmutation)
L9: Greater Spell Focus (transmutation)
L10: Empower Spell
L12: Spell Focus (necromancy)
L15: Skill Focus (Spellcraft)
L18: Greater Spell Penetration
L21: Leadership
L24: Epic Spellcasting, Quicken Spell
L27: Multispell
L28: Epic Spell Focus (transmutation)
L30: Spell Stowaway (time stop)
L32: Multispell
L33: Automatic Quicken Spell
L36: AQS x2
Get yourself a decent cohort. Using Leadership, you can have a 17th-level RW cohort who will be able to assist in your circle magic casting. See the SMACK! topic on the Rogues Gallery board herein to view some deadly smackdowns using circle magic.
Assume that this character triple-Empowers a fox's cunning spell to grant a total Int bonus of (1d4+1) x(1.5 + .5 + .5) = avg. Int bonus of +6. Your spell DCs for transmutation spells are now
10 +11 (Int) +6 (epic spell focus) +6 (archmage spell power) +18 (RW spell power) + spell level = 51 + spell level
Now, have your cohort take Leadership, and HIS cohort take Leadership, and so on. You should be able to form a circle of several participants, who should be able to boost the effective level of any spell you cast to 20th. (See FRCS, p.59). This brings your total spell DC to 71.
But that's not all! Have your cohort and cohort's cohorts Empower your fox's cunning spell further, up to 20th level. This results in an 18x Empowered fox's cunning for a total Int bonus of (1d4+1) x (1.5 +8.5) = 25 points! Your Int is now 51, for a total Int bonus of +20, bringing the save DC of your spells to 80 for the most powerful.
Here's a fairly powerful epic-level creature: an adult prismatic dragon (CR 39). Its saves are Fort +41, Ref +26, Will +41. Even with a +10 save item, this beast is unable to save against your spells except on a 20.
Get the message? Moreover, you can cast as many as four spells in a round (multispell x2) at no additional level cost (AQS x3). This should ensure a nice takedown.
Note that this character is by no means min-maxed, except as far as save DCs go. You could ditch the CWI feat (since your DM is going to be handing out items ad hoc anyway) and even ditch the Empower Spell feat, since you don't need it using circle magic.
If your DM lets you use your CWI feat (and you bought the feat, so you should be allowed to use it), craft an item that grants a +6 bonus to Charisma, put one of your level-based ability increases into Cha, and take the Epic Leadership feat (drop one of your AQS feats). With a Leadership score of around 50, you'll have a 30th-level wizard cohort who can take Epic Leadership himself (!), resulting in a veritable army of high- and epic-level wizards at your command. Using circle magic properly, you should be able to throw off four heightened/metamagicked spells of 20th effective level at 40th caster level every round. With your feats, you'll be able to penetrate the SR of a xixecal (CR 36) on a 4 or better (85% of the time). Your save DCs will hover at a solid 80 for practically any spell you can throw; the lowest-level monster in the books that isn't a devastation vermin that can save against that on anything other than a 20 is the wyrm force dragon (CR 50).
Epic Spellcasting is to create a ward against Mordenkainen's disjunction, and Spell Stowaway is to ensure that no one gets the jump on you using time stop.