The Mages' Collective are a group of magi that operate outside the restrictions of the Chantry and the Templars. Given the inherent danger in defying the Chantry (and thus risking being labeled an apostate or, worse, maleficarum), it is no shock that dealing with the Mages' Collective can be risky (if profitable) business.
Quests
At Lake Calenhad Docks
At Redcliffe Village
Justice Must Be Served/A Gift of Silence
At Denerim Market District
Other
Defending the Collective/Defying the Collective
Locations of Mages Collective Liaisons & Bags
Redcliffe Village: On the dock at the southern end of town.
Note: The Chanter's Board, Blackstone Irregulars Quest Box, and Mages' Collective Bag will not appear until after the Village has been saved.
Lake Calenhad Docks: By The Spoiled Princess tavern.
Denerim: In the Market District, behind Wade's Emporium.