Summon

Source Player Core pg. 360 2.0
Spells with the summon trait can conjure creatures, typically ones with a particular trait. Such creatures can be found in Monster Core and similar books. Unless noted otherwise, the creature must be common, it gains the summoned trait, and it must appear in an unoccupied space in range large enough to contain it. The highest level of creature the spell can summon depends on the rank of the spell, as listed below. The spell can still summon a creature of a lower level if you so choose. These rules apply only to spells that have the summon trait; other spells that call or conjure items or beings but that don't have the trait, like summon instrument, work as explained in the spell.

Spell RankMaximum Creature Level
1st–1
2nd1
3rd2
4th3
5th5
6th7
7th9
8th11
9th13
10th15