Dawnbreaker is a Daedric artifact given as a gift by the Daedric Prince Meridia upon completion of the quest The Break of Dawn.
The Dawnbreaker can be upgraded with an ebony ingot and the Arcane Blacksmith perk, however, it does not benefit from any smithing perks. This means that the weapon cannot be improved past flawless quality without boosting the Smithing skill over 100. This can be achieved by using enchanted apparel or blacksmithing potions to fortify smithing. [Source: wikia]
You can download the papercraft model here: The Elder Scrolls V: Skyrim - Dawnbreaker Sword Free Papercraft Download