[xmaerx]

It's likely just that the formula has a small window for Charisma to be useful. Mobs significantly lower level probably get squashed by the caster's CHA + resist mods versus their level, mobs with innately higher resist probably squash the CHA mod entirely, and anything outside of a specific range is subject to the goofy resistibility mods P99 deploys for anything with a stat-based resistibility modifier.

Then again, it seems like charm (and pacify) have initial-cast modifiers outside of the intended "secondary" check, with charm being virtually irresistible, and pacify resisting like mad.

I feel like resistibility in general on P99 is wonky, and different level spells should have different resist rates (low level stun versus high level stun, etc) per the "resist mods" in the spdat file. Higher level spells are Magic(0) according to the SpDat, but lower spells are almost all Magic(25).. except for charm, which is all over the place resistibility wise.