It is said that :

Shamans of old could turn to animals.

New World Elite could turn to lizards.

Vampires can change appearance.

The Demons of Goetia teach this knowledge.

An Alchemist can turrn to the divine androgynous.

The Abramelin mage had the knowledge to turn to a teenager boy/girl.

so.
What do you Anons think?
How can one truly learn this?