Both the Shapeshifter's "Shift" ability, and the Pixie's "Vanish" ability, are actually listed in the Aetherology supplement. You know, b/c Catalyst LOVES making you cross reference multiple sources to get a simple freaking answer.
Key points include;
Complex action to perform. Attributes carry over, as do any purely internal Deltaware implants, non-Deltaware implants are rejected and cause damage. Cosmetic stuff like piercings and tattooes also disappear (painlessly). You gain all non-paranormal abilities of the new form, including Armor, Natural Weapons, and Enhanced Senses (if any). Does not transform clothing or equipment, and often destroys most fabrics.