Ok, my previous wizard was miscalculated, as I was assuming Circle Magic was in play (different build for later). The Twice Betrayer Slayer, Mk II :
Spellthief 1/Bard 1/Wizard 3/Tainted Sorcerer 1/Ultimate Magus 1/Shadowcraft Mage 3/Sublime Chord 1/Ultimate Magus 2-10-Experience is a River or Item Familiar to soak up a major bloodline (any, though ideal is custom with 10 bonus feats)
-Spellthief variant granting bardic spellcasting progression from level 1.
-Caster level of 177 without gear or augmentation
Wizard = 17 + 4 + 3|24
SC = 8 + 4 + 3|15=39
Bard = 46
Spellthief = 46
Wizard = 46
SC = 39
We're built for rocket tag with the [Evil] subtype, properly buffed to always go in a surprise round. Initiative = pwnt. Activate the bead as part of the action of casting a spell, fry the TBoS's defenses with an MDJ. Swift action spell for the kill. We've got Reserves of Strength and more free metamagic than we know what to do with, especially as a Shadowcraft Mage, so make it showy
Nothing says owned like a Twinned Empowered Maximized Crushing Fist of Spite to the face of the unkillable, as they turn into a grease spot between the dukes
EDIT : Oh, and just curious...does it say what we have to do with stolen spells from Spellthief? Since I can think of a good home for all of the TBoS's spell slots before I fry him, since this build can cast metamagicked miracles out of cantrips
EDIT #2 : Quickly doing the math, the XP to buy bloodline levels is 3,000+6,000+12,000. Incidentally, exactly the amount of XP gained by investing XP in an Item Familiar. Coincidence?