80s Sci-Fi book about kid who fails magic test / woman martial artist (The Nin?) who leads revolt

Question

I need the name of a book that I read in the 80s. Here is what I remember:

• It starts on a spaceship where a young boy is being sent back to his family after failing magic school.
• He failed because he used a flame spell in response to an animal attacking him as a final test. He had been instructed to respond silently and without drawing notice to himself.
• Kids that fail are sent back with their memory erased of the time they were being trained to use magic (but something went wrong with him).
• He is recruited into a rebellion on the ship.
• The rebellion is led by a woman who does not use magic, but is so focused as a martial artist she can stand up to the magic users.
• I think her name or title was "Nin" or "The Nin".
• Toward the end of the book the boy uses his magic / mind powers to hide an underground base by shielding the persons/aliens higher thoughts and letting through only lower concerns (such as hunger, sexual desire, etc.). This makes it appear as an animal habitat.

Any ideas? I've looked forever. Thanks.

Answer 1

The book is Warrior Planet by Don Wismer.

The October Guild . . . Few knew them for what they were: an alien race from the Sculptor galaxy. Fewer still recognised their powers, or guessed their object: control of all Human Space. The Guild of Thieves . . . Its members have sworn to stop the October Ones. Their leader, the Nin Tova, teaches perfection in body--but the Thieves are helpless against the October Guild's psy powers. Asher Tye . . . An apprentice of the October Guild, he is kidnapped by the Thieves to teach them the mental skills they must have. What he finds on the Warrior Planet is not at all what he expects.

Full marks for mentioning the name "The Nin" as it was this that triggered my memory. With book ID questions I find that mentioning a character's name is usually key to jogging memories.