The Master-level is was given to students who have a lot of power. It is described as daunting and hard. The Master Magicians neither accept nor deny this claim because it deters many students from trying it.
In reality the test is for a student to entire the Fire World and defeat a challenge. Yelena's for example was to destroy the Fire Warper and then to come back with a spirit guide. A bat chose Yelena, a hawk chose Irys, a wind leapard chose Bain, and a unicorn chose Zitora.