[[WMG:The loading screen quote about turning off always run in battle was put in in the hope that players wouldn't discover how easy it is to dodge.]]
[[WMG:The Bruma Mages' Guild hall specializes in alchemy.]]
The other six guild halls specialize in a specific type of spell. There are seven magic skills, six of which correspond to specific groups of spells. The reason that the people who sell spells in Bruma don't have one specific group of spell available is because they don't specialize in spellcasting. Instead, they specialize in making potions.
[[WMG: The hero was falsely imprisoned or framed]]
The hero specifically asked Uriel "Why am I in prison?" which gives the implication s/he did nothing wrong at all. Or more likely, Uriel being the seer that he seems to be, purposely (secretly) ordered the hero to be arrested and placed in that cell to fulfill the prophecy.