After the formation of the Empire, the Emperor determined that there was a curious lack of wizards under his employ, seeing as how the only magic academy was in former Istio. To add insult to injury, the Emperor used the spoils from the conquering of Istio to fund a new College: one sitting right in the heart of Tretaria, within sight of his own Imperial Palace.
The new Imperial College of Magic was designed as a massive tower, the senior members at the top and the potential new students at the bottom. The idea was to symbolize a students progress as they climbed the floors, as your progress and power would determine which floor you studied on.
Tuition is traditionally taken care of by wealthy parents or other personal sources, though many promising students will seek grants from wealthy benefactors or even the Emperor himself.
Once the college was beginning to fill up with students, a few of the senior wizards decided to make their residence nearer the bottom, to avoid expending magic just to reach their rooms every day. In 425 ATC, some insurgents opposing the annexation of the halflings and the Empire in general decided to strike a symbolic blow to some of the most powerful and visible people in Harithma: the Senior Council, the most experienced and powerful mages in the College.
Fully half of them were killed before the assassin was stopped, stripped of his powerful anti-magic field, and executed. The assassin turned out to be a mysterious student that was recently allowed in under odd circumstances. The Emperor and the rest of the Senior Council agreed: a group as powerful as them should be harder to access. The Empire assisted in funding whatever design the Senior Council thought best and in short order a new, more modest tower was erected between the Imperial College and the Black Keep. Modest though the rest of it was, the wizards concocted a magnificent new defense for their new tower: the Steel Guardian.
The Steel Guardian is a massive snake made of shaped steel, large enough to wrap around the Council Tower from top to bottom. Its head rests near the door, and the blackened stairs are evidence of how the Guardian deals with uninvited or unauthorized guests. The Guardian was animated by the best Enchanters in the country and is a living steel titan, tasked with protecting the Council with its deadly green flames and rows of massive teeth.
No Senior Council members, once moved to the Council Tower, have been attacked since.