TRAIT - Incorporeal
An incorporeal creature or object has no physical form. It can pass through solid objects, including walls. When inside an object, an incorporeal creature can't perceive, attack, or Interact with anything outside the object, and if it starts its turn in an object, it is Slowed 1. Corporeal creatures can pass through an incorporeal creature, but they can't end their movement in its space. An incorporeal creature can't attempt Strength-based checks against physical creatures or objects - only against incorporeal ones - unless those objects have the property rune. Likewise, a corporeal creature can't attempt Strength-based checks against incorporeal creatures or objects. Incorporeal creatures usually have immunity to effects or conditions that require a physical body, like disease, poison, and precision damage. They usually have resistance against all damage (except force damage and damage from Strikes with the property rune), with double the resistance against non-magical damage.
Source: Bestiary pg. 346