Metamorphosis

Taur encyclopedia entry:
Any harbinger form can transform into any other harbinger form at any time. Form depends on necessity (ie, running faster); persuasion (ie, articulacy that differs between forms); the strong emotional state of a nearby human (ie, fear vs frostbite); or a combination of any of these qualities. The more circumstances available, the more determinate the resulting harbinger.

Necessity and persuasion often run hand in hand as persuasion can better the chances of fulfilling a want or a need.

Fatigue’s coming soon because the harbinger needs to talk to Andy and Andy is (almost always) exhausted.

Facade is an energy conservation form, for having a heavy head that impedes talking and a “front” to minimize (but not eliminate) facial expression.