Incorporeal
From AmtWiki
Description from the Dor Un Avathar
Creature is immune to all attacks except when casting magic, using abilities or otherwise interacting with the physical world. Monsters with this trait may not engage in combat except with Innate or Magic-Like Abilities. They are vulnerable to attack for three seconds after casting stops or an ability is discharged. (ex.: a Wraith with Touch of Death is vulnerable during casting and for three seconds after casting is complete and after the attack is discharged.)
