The City of Barton

The capital of the Eastern Empire, Barton is located at one end of the southern pass through the mountains.  The city is situated at the eastern side of the pass and its walls make it impossible to cross the pass without going through the city.  This is a major source of income as most merchants have to move their cargo through the city on a regular basis so they have no choice but to pay the Empire.
The city guard, often armed with wands capable of detecting magic, search everyone and everything that makes its way through Barton.  Those wishing to visit for any length of time are required to register their presence with the local government, including details on where you will be staying and who you intend to see.  If the administrators feel your answer are lacking, they have the city guard either arrest the trespasser, or escort them out to the common quarter, located just outside the city walls.
The northern portion of the town is dominated by the Emperor's palace, known simply as The Stronghold, a massive structure that is considered almost impossible to penetrate as it not only houses the royal family, but serves as barracks for their personal guards and the high ranking members of The Purge.  It also where the Emperor led the Cult from during the Battle of Voloid, which is what ultimately led to his death.
With the heavy handed guard and constant searches for magic users and the underground organizations attempting to help them, the citizen live on edge at all times.  Add in the fact that non-humans are typically treated as slaves, and that explains why there is always an air of oppression hanging over the city.
The city also hosts a once notorious prison, known as the Silent Vaults.  However, during the Battle of Voloid, the Heroes of Winterfall broke into the prison successfully, not only once, but twice, escaping with not only their lives, but with rescued prisoners each time as well.  This has obviously been a black eye to the Empire and those in charge of securing the Vaults, although recent rumors indicate that measures have been taken to address those weakness exploited by the Heroes were able to take advantage of.
Since the start of the Mage Wars, especially with the construction of a large fortress on the western side of the southern pass as well, Barton has become even more militant, with a large concentration of forces being located there to allow for easy reinforcement of those battle fronts in the east.  The Elves fear that this concentration of forces can just as easily try to push westward, so they have built several large military camps near the fortress to deal with any additional aggressions from The Empire.

The Cult of Voloid

While it was not known for much of the Battle of Voloid, it was eventually discovered that Barton served as an unofficial center of Cult activity, especially with the Emperor being one of their primary leaders in their quest to free the God from his banishment.
The Empire was able to help recruit the Shadar-Kai to the Cult's cause. This augmented their strength for a time, but it ultimately provided to be too little as the Heroes of Winterfall were able to defeat the Cult's leaders, including killing the Emperor himself. This allowed the Gods to end the threat of Voloid permanently, cutting off the Cult from their source of power. 
Thus they were defeated and it was feared for a time that the Emperor's death would plunge the Empire into civil war which was avoided when the House of Balain united to step and wield the Empire's power against the Free Lands of Men in west, spurring the Mage Wars.