It is the most powerful mace, as well as the most powerful craftable one-handed weapon in the game. One of the three Keepers in the Soul Cairn may wield a dragonbone mace, and if at a high enough level it can be taken from the body after its death.
The Dragonbone Mace requires a Smithing level of 100 and the Dragon Armor perk to create. It can be upgraded with one dragon bone at a grindstone and also benefits from the Dragon Armor perk, which doubles the improvement. [Source: wikia]
You can download the papercraft model template here: The Elder Scrolls V: Dawnguard - Dragonbone Mace Free Papercraft Download