Spell Attack Rolls
Source Player Core pg. 394
If you cast spells, you might need to make a spell attack roll. These rolls are usually made when you cast a spell that targets a creature's AC.
The attribute modifier for a spell attack roll depends on how you gained the spell. If your class grants you spellcasting, use your key attribute modifier (such as Wisdom for a mystic). Innate spells use your Charisma modifier unless the ability that granted them states otherwise. Focus spells and other sources of spells specify which attribute modifier you use for spell attack modifiers in the ability that granted them. If you have spells from multiple sources or traditions, you might use different attribute modifiers for spell attack modifiers for these different sources of spells. For example, a lashunta healing mystic with the Psychic Talent ancestry feat would use their Charisma modifier when casting a cantrip from that feat since it's an occult innate spell, but they would use their Wisdom modifier when casting infusion and other spells using their mystic divine spellcasting.
If you have the ability to cast spells, you'll have a proficiency rank for your spell attack modifier, so you'll always add a proficiency bonus. Spell attack rolls can benefit from circumstance bonuses and status bonuses, though item bonuses to spell attack rolls are rare. Penalties affect spell attack rolls just like any other attack roll—including your multiple attack penalty.
Calculate a spell attack roll with the following formula.
Spell attack roll result = d20 roll + spellcasting attribute modifier + proficiency bonus + other bonuses + penalties
The attribute modifier for a spell attack roll depends on how you gained the spell. If your class grants you spellcasting, use your key attribute modifier (such as Wisdom for a mystic). Innate spells use your Charisma modifier unless the ability that granted them states otherwise. Focus spells and other sources of spells specify which attribute modifier you use for spell attack modifiers in the ability that granted them. If you have spells from multiple sources or traditions, you might use different attribute modifiers for spell attack modifiers for these different sources of spells. For example, a lashunta healing mystic with the Psychic Talent ancestry feat would use their Charisma modifier when casting a cantrip from that feat since it's an occult innate spell, but they would use their Wisdom modifier when casting infusion and other spells using their mystic divine spellcasting.
If you have the ability to cast spells, you'll have a proficiency rank for your spell attack modifier, so you'll always add a proficiency bonus. Spell attack rolls can benefit from circumstance bonuses and status bonuses, though item bonuses to spell attack rolls are rare. Penalties affect spell attack rolls just like any other attack roll—including your multiple attack penalty.
Calculate a spell attack roll with the following formula.
Spell attack roll result = d20 roll + spellcasting attribute modifier + proficiency bonus + other bonuses + penalties