When I played 2E, we had 2 divine caster characters who were of the same deity. At times, they would cast the same spell (eg. disple magic or flame strike), with one "channelling" his divine energy through the other, effectively creating a spell with a caster level equal to those of both character's caster levels combine. Thus, 2 same relion clerics (level 10 and level 13) cast a "channeled" dispel magic with an effective caster level of 23rd level.
We even did this with arcane casters too, but they had to be of similar alignment.
My question is, is there anywhere within the PF rules, feats, etc. that allow this to take place legally? Or is this simply a flavor thing that has no rule basis in PF or even 3.5? Just curious.
Despite what I just wrote, I think we only allowed the use of it for high level characters, 15th+. It's been so long ago.
There's something like that in the 3.0 splatbook Tome and Blood, which probably means it's in Complete Arcane or one of the 3.5 books too. It's a metamagic feat that lets you cast a spell with another spellcaster that has the same metamagic feat/metamagic'd spell, +2 to save dcs and +1 to caster level checks to beat SR for the first additional caster, and +1 to dcs and sr checks for subsequent additional casters. Use the highest base DC among the casters.
It's basically just for combat, as the wording doesn't seem to let you up the caster level check for anything other than SR.