Shapeshifting

Shapeshifting  is the ability of an entity to physically transform into another being or form.

Confirmed:

 * Mystique (X-Men series)
 * Annabelle Sullivan (Crossover Universe)
 * Kyle Sullivan (Crossover Universe)
 * Ghosts (Crossover Universe)
 * Vampires (Crossover Universe)
 * Vampires (Gravesville Intermediate)
 * Sirens (various media)
 * Courage (Courage the Cowardly Dog)