Q155: It's the Master Spellthief return. My DM and I are currently locked into a little argument about the viability of Sublime Chord + Master Spellthief abuse.
My argument:
The end result is X * Y (where X is your SC caster level and Y is the number of arcane spellcasting classes you have levels on).
His argument:
The end result is X, because Master Spellthief adds your levels in Arcane spellcasting classes together, NOT your CL in each of those.
I'm sure there was something that shot THAT counterargument down, but I cannot for the life of me remember what it was.
A 155
Strict RAW -- it does say "levels in arcane casting class" ... not "caster level"
I was sure there was something to the effect of arcane spellcasting levels and arcane caster levels being interchangeable.
I'd love to hear it if it exists, but it strikes me as a bit silly to argue strongly for the ridiculously imbalanced implementation when there's a plausible argument for the balanced one.
AHEM. I'm EXPLOITING IT HERE!!
Eh, well, it still seems pretty ironclad since it doesn't say "arcane spellcasting levels", but actually spells out that they must be "her levels in another arcane spellcasting class". Which means either Orange Ioun Stones make you level up in Wizard, or they're not the same. Also, strictly speaking, it debuffs you if you've taken any levels in a class that grants "+1 level of spellcasting" or somesuch prior to Sublime Chord, because you can't count them (you only count the actual levels, and you only get a single class because it uses the singular). Although if you have more than 1 base class, Master Spellthief converts it into a buff (Bard 1/Wizard 8/Spellthief 1/Sublime Chord 1 adds Sublime Chord and Wizard to get 9, Bard, Wizard, Spellthief and Sublime Chord are set to 9 each, and then you add them to get 36 through master Spellthief).
EDIT: I think that may actually have been what you were going for.
EDIT^2: What you can't do, however, is the following; You can't be a Bard 1/Wizard 8/Spellthief 1 and take Sublime Chord 1, and say your CL is 10 thanks to Master Spellthief, so your Sublime Chord is 11, so all your classes are set to 11, so Master Spellthief sets them all to 44. There are more brutal abuses than this that have been argued over elsewhere, but which rely on basically the same misinterpretation.