☆ animagus registry

An Animagus (pl. Animagi) is a witch or wizard who can morph him or herself into a specific animal at will. It is a learned skill that takes studying and practice to perfect and cannot be learned over night. All known animagi take the same form as their Patronus. 

Only very powerful and skilled wizards are able to become Animagi. The process of becoming an Animagus is long and arduous, and has the potential to backfire and cause the transformation to go horribly wrong. Once the initial training is over, an Animagus can change at will at any time, with or without a wand. Animagi can only take on the form of one specific animal. This animal form is not chosen by the wizard, but determined by their personality and inner traits. Thus, one's animagus form is a reflection of one's inner nature. Animagi can NOT take the form of a more "magical" creature. Each Animagus bears an identifying mark on their animal form that is caused by something on their human body. This may be a physical trait like dental structure, or an acquired trait such as glasses. If an Animagus undergoes a major physical change, such as the loss of a limb, their animal form will also reflect that. Also, an animagus in animal form will retain the lifespan of an ordinary human being. In addition, an Animagus will appear to lose their clothing upon morphing. The clothing will reappear upon reestablishing the human form. 

The difference between mere Transfiguration and the Animagus morphing ability is that an Animagus can change into an animal whenever they want, without a wand or an incantation. Being an Animagus is an ability, and Transfiguring requires a spell. An Animagus still thinks as a human does when they are in their animal form. However, an Animagus's feelings are not as complex when they are in their animal form. An Animagus also has the ability to to communicate with normal animals. There seems to be a clear understanding of want and need in this communication ability, but the full extent and quality of it is unknown. There is a particular spell which creates a blue and white flash that will force an Animagus out of their animal form. 

It is also important to note that a werewolf is fundamentally different from an Animagus. Lycanthropy is caused by a blood infection transmitted through the bite of a werewolf, whereas the Animagus skill is learned. The werewolves cannot keep their minds after a transformation (unless they take the Wolfsbane Potion), nor can they control when they wanted to transform, while Animagi can do both. 

Every Animagus is required to register with the Ministry of Magic at the Improper Use of Magic Office. This registration includes revealing one's animal form and one's distinguishing markings. The Register is available to the public. The penalty for failing to register as an Animagus is a sentence in Azkaban, though the length of time is unknown. Due to the complexity of the magic involved in becoming an Animagus, they have become very rare.There was a total of seven registered Animagi in the twentieth century. It is also partially because of this complexity, in addition to the danger involved, that Animagi are required to register themselves.