John Childermass

John Childermass is one of the secondary characters in Jonathan Strange & Mr Norrell. He is the manservant of Mr. Norrell and his counselor (often advising for a better path than that which Mr. Norrell wants to choose), he helps his master and protects him and his vast collection of magical books.

Personality
Childermass is very independent (which sometimes clashes with his role as servant), intelligent, pragmatic, reserved, solitary, and a behind-the-scenes strategist (he's the one who pushes Norrell to go to London).

He is loyal to those he chooses, even if secretly in some cases (the Raven King), sometimes at the risk of his own life. He proves throughout to be brave and stoic about physical pain.

He is often sarcastic, especially snarky towards those of a higher social position who see those of a lower one (as Childermass himself) as lesser humans.

Abilities
Throughout the series he gave multiple proofs of being himself a magician, having knowledge and at least some amount of inborn ability for magic, performing certain spells like Belasis' Scopus, making himself into a shadow against a dark wall, sensing when others do magic, telling the future or finding out information about people's past or present with his tarot cards; in the discussion with Jonathan Strange in ep.05, he shows theoretical knowledge about spells and enough about the Raven King and Faerie to make correct suppositions about where the roads are and what's going on.

This knowledge was acquired by reading from Norrell's library, to which he had more access even than Strange and for a longer period. He is shown multiple times with a book in hand. Being a servant, Norrell sees him as his inferior and doesn't perceive him as a threat; that and Childremass' secrecy about his own abilities and interest made his master not impose on him the restrictions he imposed on his own pupil.