Help remembering a PrC that allows you to cast an Arcane & Divine Simultaneously

[Xarteros]

Can't remember much, but I remember the class gave some form of ability to cast an Arcane and a Divine spell at the same time. I think they might have had to be the same spell, so it might have been limited to spells that appear on both spell lists, but IIRC it was basically a way to get a free Twin spell effect, but using up the slot on each class instead of modifying it with Metamagic (Also, I assume having Twin Spell on both copies of the spell would make it a quad-twin spell, which is what I'm looking it up for)

Can anyone help point me in the right direction? I've been looking everywhere and just can't seem to find it for the life of me.

[El Dorado]

Sounds like Pathfinder's Mystic Theurge PrC or Kobold Press's Theurge.

[Xarteros]

Sounds like Pathfinder's Mystic Theurge PrC or Kobold Press's Theurge.

The Pathfinder one actually sounds like what I was remembering =/

Thanks for the quick response =)