Mystic theurge cheese

[mehs]

I remember a player in a campaign playing mystic theurge and using an unholy amount of cheese to get stuff like a caster level of 20+ at 11th or so level. I can remember if this was 3.5 or Pathfinder, but it was one of those. Can people tell me the cheese that was likely used to pull those shenanigans?

[Kelb_Panthera]

Probably consumptive field shenaningans. The only non-cheese (as in a thing simply functioning as intended) way to achieve such CL is through the circle magic feature of a handful of prestige classes and a feat in a very obscure source, none of which comes online by ECL 11, IIRC.

There's a couple domains that give big boosts to the CL of divination only.

Maybe if you give us a little more to go on? MT doesn't really do anything except allow otherwise difficult spell combos. It could be just legitimate CL optimization through a host of minor items and effects that stack, although +9 or more is a bit extreme.

[sleepyphoenixx]

There's a feat in Dragon Compendium called Elemental Theurgy that lets you combine the CL of all your caster classes with spells of one the elemental descriptors, but only for casting spells with that descriptor (fire, water, air, earth). Unfortunately it doesn't apply to [cold] or it could be used with Snowcasting (FrB).

There's also a similar feat called Aligned Theurgy in Dragon Magazine (322 iirc) that does the same thing with alignment descriptors - that one can be cheesed trivially just by casting Mark of the Enlightened Soul (DrM) or using several other options to give all your spells an alignment descriptor.

There's also the Psiotheurgy feat (also from Dragon Mag, but i forgot which) that does the same thing for arcane/psionic theurges, but only for one school.

You could also just take a look at Raising Caster Level (http://www.giantitp.com/forums/showthread.php?444635-Raising-Caster-Level).
CL 20 at level 11 isn't trivial but doable within WBL i think. You don't need to be a theurge for that though.