| There are a couple of things here. First some of the spells are only available if you are the right class, like sorcerer (among others).
The ice nove and ice ball are bought from Grymlock at his tower in the Northern lands.
The fire nova, blast nova, magic missile and some others are bought from the wizard in Fargrove.
As far as I know the ice storm, fire storm, cataclysm and some others are not in the game. Maybe they will be in a future release (patch or expansion) of the game. | 
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