The Dungeon DLC update adds the Firesong and House Mornard motif achievements and the style materials (Firesong Skarn and Vibrant Tumeric respectively), but it will take a few months for those to actually drop from the Galen Delve and World Boss Dailies and Galen's Volcanic Vents. Keep an eye for the Crown Shore Showcase articles, as it can tell the actual dates for when the motifs drop.