The master badge for all the schools requires you have all spells up to DS. You need to find all the secret trainers to find your spells (one on colossus boulevard to the left of Mindy Pixiecrown, one at digamore station to the right of Sherlock Bones, one at WC fair grounds, and one at the Krok Secret Shop). The tricky one is the myth spells found in the Krok Secret Shop area. In the oasis, look for two tall obelisks with a circular sigil sitting between them. When the obelisks are completely lit up (you may have to wait a while for this to occur), use the sigil and on the island you will find a spell vendor that has your missing spells.
P.S. You do not need to get Medusa, this badge is for all the spells up to level 48. Beyond the listed spells from Cyrus, this would be Troll Minion, Stun, Pierce, Orthrus, Myth Blade, Myth Prism, Minotaur Minion, Golem Minion, Cleans Ward, and Blinding Light, Myth Shield, and Myth Dispel. I believe that this is the full list. Cannot get into the game to check my myth toons.