Kbd heads is a rare drop from the King Black Dragon. It can be combined with a slayer helmet or slayer helmet (i) to create a black slayer helmet or black slayer helmet (i), respectively. Doing so requires purchasing the ability King black bonnet for 1,000 slayer reward points.
It can also be split into three ensouled dragon heads by using a knife on it. In addition, it can be stuffed and then mounted in player-owned houses in the Skill Hall at level 78 Construction, but it is a one time use and it cannot be reclaimed.
Before the King Black Dragon head can be mounted, it must be taken to the Taxidermist in Canifis. She will charge 50,000 coins and turn them into stuffed kbd heads. They can then mount it in their house at level 78 Construction using 2 mahogany planks and 2 gold leaves. Mounting the Kbd heads will grant the player 200 Attack, Strength, Ranged, Magic, and Defence experience, thus it is highly suggested for pures to not do so.
When you take it to the Taxidermist, she will exclaim “This must be a King Black Dragon!” and then “I’ll have to get out my heavy duty tools — this skin’s as tough as iron!”