There are a number of mortals that can manipulate supernatural forces via various mystical traditions. Some of them are powerful enough to battle a Kindred head-to-head, particularly if given time to prepare ritual magic. It is uncertain how many are present in Atlanta, as the term “Arcane” originates with the Wise.
While there are no specific accords with magi in the city, they tend to leave Kindred alone if left alone and claim little territory that the Camarilla is interested in. Kindred of the city are not barred from antagonizing them if the situation demands it, but should avoid doing so for the safety of others if at all possible. Many sorcerers seem content to be left alone to research, but leap into action to burn to ash any clear and present threats to their security.
When in doubt, contact the Tremere to investigate further (a boon will be owed).