Unless I am comfused, I think you are talking about the Fire Legion event quest, unless there is another quest that I don't know about there.
It is only obtainable with a GM activates the event.
You will see it announced in system (red) chat when it has been activated. You can then pick up the quest from the Village Spirit in Dreamweaver Port (only appears during the event).
It is usually run at least every two days, sometimes everyday.