Hester is the leader, often being top in ranks and known to be an "illustrious witch".
Anadil is the "sidekick" or second best to Hester although she is also top in the ranks.
Dot is known to be the most passive of the group although she is more nice to Sophie at the beginning then both of the other two witches.
The coven has been in all four books as antagonists and protagonists at the same time. The coven is in the Ever Never handbook as Hester writes tips and tricks for Nevers.
The three witches are in the School for Evil and are currently trying to find a schoolmaster as their quest in book four: Quest for Glory.