right, this tactic depends heavily on interpretation, but could be quite powerful.
Human Nec 5 / Red 10 / Acm 5.
Dropped: Evocation, Conjuration (needed schools: Divination, Necromancy, Transmutation)
Feats:
Tattoo Focus
Quicken Spell
Craft Wonderous Item
Craft Arms & Armor
Spell Focus (Necromancy)
Spell Focus (Something Else)
Skill Focus (Spellcraft)
Leadership
Greater Spell Focus (Necromancy)
Equipment:
Crafted:
Headband of Intellect +6
+3 Mage Robe of Haste
+5 Mithril Buckler Proof against Transmutation
+1 Boot of Spellsword (x9) (Undeath to Death, Dispel Magic, Greater Dispel Magic, Dominate Person, Dominate Monster, Charm Person, Charm Monster Hold Person, Hold Monster)
+1 Boot of Spellsword (x9) (Enervation, Energy Drain, Heal, Cure Light, Moderate, Serious, Critical Wounds, 2 other nasty spells)
Phylactery
8 +4 Keen Vorpal Scimitars.
Bought:
Greater Rod of Persistant Spell.
some 1000 GP diamonds.
Darkskull
Cohort:
Human Wizard 19 (with Multiattack and Multiweapon Fighting quickdraw, improved critical (scimitar))
Tactic:
Start by casting a Persistant Duplicate and let your Cohort cast Persistant Duplicate. Then, use the Circle Leader feat to give you +180 (or so) spell levels from your Cohort. This cohort can't cast anymore spells, but that doesn't matter. First boost your Effective Level to 40 and your Caster level to 40. You have 140 levels left.
Cast Gestalt on you, both Duplicates and the cohort. You are now 1 creature with 8 arms (hence the 8 scimitars, and because of the Druids feats, you can use them all without penalty).
Cast Persistant Tenser's Transformation (BAB as 40th level fighter, or at least, as 20th level).
Cast Mind Blank
Cast detect magic (to detect antimagic fields).
Take two doses of Paneolo (raise DC by 3, take 2d6+2 Cha damage, but you're Undead, so forget that damage

)
You now have two options:
1) Cast Two Minds, then cast Time Stop, then, start wasting your enemies with "Empowered, Empowered, Empowered, Empowered, Empowered, Empowered, Horrid Wiltings" (you can cast a lot of these due to Circle Magic. The DC is insane (high forties)).
2) Kill things with your scimitars (BAB = +16 / +16 / +16 / +16 / +16 / +16 / +16 / +16 / +11 / +6 / +1). Of course, you're Improved Invisible, so that's another +2 and no dex bonus for the opponennt and we haven't even counted Str mod...
Of course, you have some Mordenkainen's Disjunctions, so you can destroy Anti-Magic Fields (40% chance!). Also, "nonesuch Spell: Antimagic" field may help against that troublesome spell.
That's pretty much unbeatable...
To check this, you need:
PHB, DMG, FRCS, MoF, BoEM2, LoD, T&B, MotW, R&R, DotF.