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A Thaumaturgist is a Mage that prefers chaos to order. As such, they tend to learn random spells, and since attacking something creates more chaos than anything else, every spell they learn is an attack spell. They have no need for spell-books, as they harness the spells from within themselves. However, they also have no ability to improve the power of a particular spell - once learnt it will remain at the same strength for ever. Likewise, they also have no ability to control what they learn, and some of their spells will cause them damage (like darkness spells blinding them if they do not resist darkness).
For more information on Thaumaturgical Powers see this page Starting stat modifiers, starting Skills, innate abilities and starting equipment: Please see the in-game help.