My level 17 wizard took out multiple mindflayers, solo. I needed the rest of the team up until then, just to be sure I wasn't being overconfident, but I happened to have a scroll of Wish that I copied into my spellbook, and I took Unfailing Missiles, and Mind-rape, (for counter spelling purposes only. I don't play evil characters,) as my level 17 spells.

Unfailing Missiles was designed by me.

Level 9 Wizard Spell

Components: V, S

Casting: duration: instant

Range: Long 400' + 40' per caster level. (1080' @ Lvl 17)

Unfailing Missiles gives the caster 3 "lances" of energy that may be directed at any three targets that are no more than 20° apart. The caster can also direct multiple lances at any single enemy. Each lance does 17 d6+1 points of sonic and force damage split 50/50. There is no saving throw. If you can see it, it gets hit.

I was a bit irritated that Magic Missile was the only spell that was guaranteed to hit. The DM capped the spell at 17 d6+1 with no level scaling because he was already having difficulty designing encounters that the group was having any difficulties with. He did allow the range to scale normally, so with magical glasses I could eventually hit shit at well over a quarter of a mile.