^Another_Poet:
If it's an arena combat, trap based attempts become impossible. Of course, there's a certain element of cheese in those so...

Also, can't I just buy a candle of invocation? I'll eat the 20x cost, even after you add in the 5000xp cost the writers seemed to have forgotten about. (either by paying 25k gp or by losing 1 feat)
Even with the insane pun-pun esque potential of the candle, I'll just be summoning my target balor with it. IE. almost RAI
(I'm trapping and killing the summon instead of getting an ally, so not quite As Intended)

The cleric who's in charge of the candle (or the as-yet-unspecified gate process) will be oriented to buffing cha checks. There also needs to be one artificer to get a scroll of Dimensional Anchor (since it's a 4th level spell).