Mages of Faeo, there are great news for you as an item has appeared in Sheara’s treasury that will make your life much easier: the Ziccurat of Secret Power.
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With the ziccurat you can now easily change your school of magic by selecting the wanted school from a dropdown menu. Spells that you have already learned will not get lost.
 

Speak to  Striagorn or  Erifarius to get to Sheara’s Spectral Expanse and obtain the Ziccurat of Secret Power in the treasury. The Ziccurat can be obtained by mages  with a reputation rating of at least 900.