In what ways could you reveal plot or background by having unusual effects become apparent through the death and replacement of a spirit guide, witch's familiar, or the like? As an example, from my table, the Magical Child archetype of the Vigilante:
Animal Guide (Ex):
A magical child starts play with a magical spirit guide in the form of a familiar, using her vigilante level as her effective wizard level. The familiar also has a social identity as a seemingly normal animal, though vigilantes with outlandish familiars might still need to hide the familiar.
At 3rd level, the magical child’s familiar reveals another aspect of its form, and its vigilante identity changes into a creature on the Improved Familiar list...
If a magical child’s familiar dies, its consciousness simply leaves its body, and the magical child can replace its body after 24 hours. To do so, she must conduct an 8-hour ritual that costs 200 gp per her vigilante level, but once the ritual is complete, the familiar returns in a new body. It retains all of its memories from its earlier service to the magical child....
This kind of sounds like a related but not identical process to the soul anchor.