Ensouled heads are items that can be dropped by their respective monsters. These heads can traded in to Nieve the Slayer Master in return for a fair amount gold.
Nieve the Slayer Master can be found just outside of ;;Shops.
Wearing the imbued ring of wealth will increase your chances of obtaining ensouled heads.
Ensouled Impling Head - 50,000
Ensouled Scorpion Head - 50,000
Ensouled Dog Head - 50,000
Ensouled Chaos Druid Head - 50,000
Ensouled Giant Head - 75,000
Ensouled Kalphite Head - 125,000
Ensouled Cave Horror Head - 150,000
Ensouled Dagannoth Head - 150,000
Ensouled TzHaar Head - 150,000
Ensouled Demon Head - 175,000
Ensouled Bloodveld Head - 200,000
Ensouled Abyssal Demon Head - 225,000
Ensouled Dragon Head - 250,000