[Loredweller]

Sorry, not completely true. Their base, IMHO, is Argonian Mission in Ebonheart, and Lady Dren sems only to be their representative in relations with humans and elves. I've got an impression it's pure Argonian order, at least i've never met a single NPC of non-Argonian race admitting the membership of Twin Lamps (and just everybody in the Mission without that bracelet on the hand is a proud member of Twin Lamps). You can never got a single quest there nor you can officially join them, however, although you may have a chance to deliver some runaway slave here on occasion.