Breath of Zehir
The Onyx Dragonshard is attuned to the Acid and Force keywords. This Dragonshard has a +3 enhancement bonus and is equivalent to a Level 15 magic item.
During a short rest, you can install the Dragonshard into a weapon or implement. Add the Dragonshard’s enhancement bonus to damage rolls for attacks using the weapon or implement that have the keyword the Dragonshard is attuned to. In addition, these attacks ignore the resistances of dragons for these keywords.