Upon Ardan's surface 10% of the world's population are capable of using magic. These users enter into magician's guilds to improve their skills and gain access to requests, jobs exclusively requiring the skills of a magician.
The idea is for there to be a single guild (name unknown as of yet) where the characters are either about to join or are already members. All magicians must be part of a guild or else they will be hunted down or are killed by their own magic (guild symbols allow someone to regulate their own magic so are no longer a danger to themselves and those around them).
Within the guild characters can form teams or work solo (multiple characters per person are allowed). Requests will be submitted to the Guild Master (played by me) in the OOC or by PM for approval. Once approved a list of available requests will be listed in the OP of the OOC. Once taken the request cannot be accepted by a second person (although nothing stopping someone from going to 'help' out another).
Magic is fairly free but there are obviously limits (the source of magic will be partially dependent upon physical stamina, especially if it's physical improvement magic). There will also be inter-guild events.
This is my idea so far, I'll probably need to clarify points along the way so feel free to suggest/query anything.