A Wizard20 could probably win this scenario. Since you have more resources, I recommend this:
Dragonborn Gray Elf Generalist Wizard3 (
Transmutation Domain/War Weaver5/Spellguard of Silverymoon5/Initiate of the Sevenfold Veil7/Incantatrix10/X5.
(Get into War Weaver via
Complete Arcane's Sanctum Spell feat.)
This gives you
plenty of spellcasting and spiffy party-boosting abilities. For your 5 remaining levels, you could go Escalation Mage (
Faiths of Eberron) and get Shadow Haste, so you can Quicken or Extend 5 spells per day. You also get your CHA bonus to HP once, at Escalation Mage1. (
Auto Quicken, when taken 3 times, removes most the need for Escalation Mage. If you go this route, more Incantatrix levels would help.)
Taking a level or few of Warblade (
Tome of Battle 20) or/and Swordsage (
Tome of Battle) would get you spiffy swift/immediate action maneuvers. (
Maneuver cards are here.) White Raven Tactics is
wonderful, even if you can't use it on yourself! The Diamond Mind maneuvers Mind Over Body, Action Before Thought, and Moment of Perfect Mind let you use a Concentration check instead of a save, and you don't auto-fail on a natural 1. (Save 'em for when you want to guarantee a successful save.) The Iron Heart maneuver Wall of Blades lets you use an accuracy roll instead of your AC against one attack, which may be higher at this level. The Shadow Hand maneuvers Shadow Jaunt, Shadow Stride, and Shadow Blink are extraordinary (non-magical) means of teleportation!
Legacy Champion (
Weapons of Legacy) would let you apply up to level 9 spells in your tapestry.
Shapechange your party into Chronotyryns (
Fiend Folio) for flight and two turns per round! Alternate between that and
Choker form for an extra standard action per round!
As for "Epic" abilities,
Exceptional Deflection and
Infinite Deflection mean you're just plain immune to ranged effects that target you and require an accuracy roll.
All of them. Add in
Reflect Arrows to humiliate enemy attackers. If you go this route, a Monk2 or/and a Fighter2 dip is probably worth it for the feats.
If you're playing at this level and your GM isn't coddling you, then
you need immunities! Specifically, become immune to these:
-[Mind-Affecting] abilities.
Mind blank is a common spell for this, but if you become a creature of the Undead or Plant type, you're set!
-[Death] effects, and if you can, also negative energy.
Death ward, Soulfire [+5 armor/shield enchant] (
Book of Exalted Deeds), and Undeath help here.
-Movement-impairing effects. A
ring of freedom of movement is probably best.
-
True seeing. Because being fooled by Illusions sucks and you can afford a mask of this. (It's 75K and from
Unapproachable East.) Additionally, having blindsight (such as from the Diamond Mind stance Hearing the Air) also helps. Go ahead and get both!
-You probably don't need a
ring of universal elemental immunity, but when you're this epic (and therefore, this rich), why not?
You'll also need flight, such as from Chronotyryn form, the
fly spell, a Winged Mask (
Magic of Faerun), whatever.
The
Affiliations and Magical Locations Handbook will help a bit in getting the best locations. (
Complete Scoundrel's Otyugh Hole is probably the best.
Complete Mage's Metamagic Storm, Rainbow Falls, and Shieldstone Cavern are also spiffy.)
At epic levels, buffs work. Most other things don't. Focus on buffing your teammates (and yourself) and winning the fight in the first round (or the surprise round, if you can). (The technical term is 'rocket tag' due to the squishy nature of the creatures and the very dangerous nature of the attacks.) See
The Seven (7) Facets of Character Optimization for general ideas.