Mistress Tannis was a very attractive Omwati Jedi Master and leader of the Teyan Praxeum during the Old Republic. With rich, blue skin, feathery hair, and indigo eyes, Mistress Tannis possessed a strong ability in the Force, as well as a deep understanding and knowledge of the traditions and ways of the Jedi. Successor to the leadership of the Teyan Praxeum, Mistress Tannis took the position when only a single member of the founding Jedi of the school remained, Jedi Master Willm Lwyin.
Directing the activities of the school, Mistress Tannis oversaw the school's curriculum as well as the duties that kept the Teyan Praxeum a self-sustaining colony. Housing forty Jedi students, as well as nine other Jedi Knights serving as teachers, the school focused on every aspect of becoming a Jedi Knight. In the mornings, Mistress Tannis and the teachers oversaw the teaching of skill exercises such as exercise, telekinesis, and lightsaber combat. Mistress Tannis believed always believed in study and knowledge of the history and customs of the Jedi because she believed that knowledge of the past was important to avoid making the mistakes that were made in the future.
As was such, the afternoons at the school were devoted to academic studies. Also, a separate part of the school was used to train those students who were nearing the end of their education. Known as the Cave of Truth, it was used as a final test to Jedi Knights. Designed by the original founders of the school, the Cave presented the Knights with images that would test their confidence in such areas as patience, fear, greed, and anger. Over the years, Mistress Tannis saw many Jedi Knights graduate from her Praxeum and join the ranks of the Jedi to preserve peace and justice throughout the galaxy.