A dragon scale can be found on a High Dragon found at the Mountain Top during the quest for the Urn of Sacred Ashes. Slay the High Dragon and you will find a Dragon Scale on its corpse. Bring it to Wade at the forge in his shop, Wade's Emporium in Denerim.
RewardsWade's Heavy Dragonscale armor set
Dragonbone (Tier 7)
+35% fire resistance
Set: -20% fatigue