How did Sirius Black turn into a dog in Ascaban without a magic wand?

Sirius Black was able to turn himself into a dog without a magic wand due to his Animagus transformation. An Animagus is a wizard or witch who has achieved the rare ability to transform into an animal at will. This is done through a magical process that requires an extensive amount of practice and dedication.

First, the Animagus needs to spend a significant amount of time studying the magical arts and researching the specific animal they wish to transform into. They must then create a potion that contains a variety of magical ingredients, such as a hair from the desired animal and a drop of their own blood. After drinking the potion, the Animagus will be able to transform into the desired animal at will.

Sirius Black was an Animagus who was able to transform himself into a large black dog. He used this ability to escape from Azkaban prison, where he was being held for a crime he did not commit. By transforming into a dog, he was able to slip past the guards and make his way to freedom.