He is a hero, and fights all sorts of monsters including the Daleks, the Cybermen, the Sontarans and the Judoon . The League is about to send him a memo asking for him to join, but it probably hasn't arrived yet. Despite this, he has sent his reply. Thats Time Travel for you!
Because he is a Time Lord, he has two hearts and can regenerate himself to heal wounds, at the cost of changing his face. Each Doctor has their own unique personality but all are driven by one goal - to save people in trouble, defeat monsters, stop alien invasions and run for their lives. Each incarnation of the Doctor is different, with all of them having their own way of bringing peace and unity to the Galaxy using non-violent methods, only resorting to violence when absolutely necessary. However, one incarnation of the Doctor, the War Doctor, was a battle-hardened warrior who fought in the devastating Time War.
He owns a wonderful machine called the TARDIS, which he lends to Radagast the Brown occasionally. The Doctor also has an arch-nemesis, another renegade Time Lord called The Master, who has insanity to rival that of some ofthe League's greatest Leaders...