| Grick |
Generally if there's a variable statistic, you use the one your casting is based off of. A witch would use Int, while an oracle would use Cha. This is not specified anywhere in the rules, so YMMV.
When a spell only lists one specific statistic, like Spiritual Weapon using your your Wisdom modifier, then it's always Wisdom even if you're a Cha- or Int-based caster.