Questions of Derpitude

[Digeridew]

Q#1. What is the resulting caster level of the following build?
4 Spellthief, 1 diviner, 2 Unseen Seer, 10 Ultimate Magus, 3 Mystic Theurge

Master spellthief feat taken, as well as practiced spellcaster Diviner, and practiced spellcaster spellthief. Race human, do not include any magical items or any thing of that nature please.

Q#2. Utilizing the above build, is there a damaging spell it can cast that makes use of the resultant caster levels?

q#3. Does said build "break the game"? ((I know, opinion question, feel free to disregard))

[Keld Denar]

Mystic Theurge wouldn't do anything here. Both ST and Diviner are Arcane (as they have to be for UM).

Your CL will be pretty ridiculous. Don't forget to Persist Cloud of Knives to use that REALLY high attack bonus, on top of whatever else you do.

The only uncapped spell I can think of off the top of my head is Wings of Flurry, which is Sorcerer only. You could poach it, I think, with Wyrm Wizard or Recaster, but that would cut in a bit to your UMness.

[Digeridew]

You're right. I'm fighting a horrific migraine. If I exchange MT for more US what are my end caster levels?

[Saidoro]

It depends on how the advancing classes interact with the spellthief's "At 4th level and higher, a spellthief's caster level for spells is one-half his spellthief level." line. There's probably an official ruling on this, but I cant say I know what it is. Also, it depends on whether practiced spellcaster applies before or after master spellthief.
|Half Advancement|Full Advancement
Practiced First|26|32
Master First|20|24
You'd probably better off sticking with one class to get higher level spell slots and just metamagic your spell of choice up. Alternately: Spellthief 4/Sorcerer 1(Use Early entry tricks for 2nd level casting)/Bard 1/Wizard 1/Dread Necromancer 1/ Beguiler 1/Wu Jen 1/Ur-Priest 3/Mystic Theurge 7(Advancing Ur-Priest and Sorcerer) gives you this table for Ur-Priest
|Half Advancement|Full Advancement
Practiced First|47|47
Master First|19|19
And a single Orange Prism Ioun Stone will boost that to 51. Take note of Blasphemy (http://www.d20srd.org/srd/spells/blasphemy.htm) and Friends.

[Keld Denar]

Needs more Sublime Chord...

[Digeridew]

you always choose what order feats and such are applied.