Clanbook: Followers of Set Revised с. 67
Shadow of Apep (Serpentis 9)
Only Set and Set's own childer can perform this terrifying power. These ancient monsters can take the form of Set's defeated enemy, Apep. The vampire becomes a giant serpent of fluid, glittering Darkness - not mere shadow, but anti-light, like the black force commanded by Obtenebration. In this form, physical force cannot harm the vampire: not claws or fangs, not bullets not explosions, not anything except fire, sunlight or magic. Physical barriers cannot easily stop the vampire, whose shadowy form can seep through even the tiniest crack. The vampire, however, can still exert physical and supernatural force quite freely.
System
Taking the form of Apep costs a Willpower point; the vampire stays in this form for a scene. The transformation takes three turns to complete. In this form, the vampire takes no damage from any physical attack: fists, weapons or falling buildings pass through the vampire as if she were a shadow. Fire and sunlight inflect the normal aggravated damage, however, and magic still affects the transformed vampire. The vampire itself gains three dots in each Physical Attribute. Ignore generational limits for this purpose, so the vampire could have Strength, Dexterity or Stamina greater than 10. The transformed vampire can use its Strength to make normal close combat attacks and can bite for Strength +2 dice of damage. The vampire can also employ any Discipline that does not require hands.