In Al'Kabor's Nightmare: Dagda Icefury plays a role in the group task "Catastrophic Power" as well as the raid expedition "At World's End" (see the links for event and loot information).
In Brother Island: Dagda Icefury (click for map image) is found on the southeastern corner of the island. She also appears in the mission "The Cover of Night" (see this quest entry for details).
In the Caverns of Endless Song: Dagda Icefury (click for map image) is found in the eastern caverns, in between the spineback caves. She also appears in the mission "Two Sides of the Shield" (see this quest entry for details).
In Arx Mentis: Dagda Icefury appears in the mission "All Rivers Lead to the Sea" (see this quest entry for details).