Summoner Spellcasting

Your link to your eidolon grants you limited magic connected to your eidolon's nature. You are a spellcaster and can cast spells using the Cast a Spell activity. As a summoner, when you cast spells, your incantations call upon forces related to the spellcasting tradition determined by your eidolon, and your gestures often echo the shape of the rune that you and your eidolon share.

Each day, you can cast one 1st-rank spell. You must know spells to cast them, and you learn them via the spell repertoire class feature. The number of spells you can cast each day is called your spell slots.

As you increase in level as a summoner, the magical link with your eidolon grants you additional spell slots per day, as well as higher ranks of spells. Your total number of spell slots and the highest rank of spells you can cast are shown on the Summoner Spells per Day table.

Some of your spells require you to attempt a spell attack to see how effective they are, or have your enemies roll against your spell DC (typically by attempting a saving throw). Since your key attribute is Charisma, your spell attack modifier and spell DC use your Charisma modifier.

Heightening Spells

When you gain spell slots of 2nd rank and higher, you can fill those slots with stronger versions of lower-rank spells. This increases the spell's rank, heightening it to match the spell slot. You must have a spell in your spell repertoire at the rank you want to cast it in order to heighten it to that rank. Many spells have specific improvements when they are heightened to certain ranks. The signature spells class feature lets you heighten certain spells freely.

Cantrips

Some of your spells are cantrips. A cantrip is a special type of spell that doesn't use spell slots. You can cast a cantrip at will, any number of times per day. A cantrip is always automatically heightened to half your level rounded up—this is usually equal to the highest rank of summoner spell slot you have. For example, as a 1st-level summoner, your cantrips are 1st-rank spells, and as a 5th-level summoner, your cantrips are 3rd-rank spells.