Cole's Crystal

Elements
Cole's crystal contained the elements of Fire and Paper. Using both together was dangerous as it could catch up to the user. If the paper was stuck to an enemy it could easily kill them.

Owners of the Crystal
1st: Cole Peters: (From Book 2 to Book 3.) Cole is the original owner and received his crystal at birth.

Current: Kai Muromi: (From Book 3 to Current) Kai received the crystal after Cole's final wish was to give it to him. Cole knew that Kai was actually an Akermota and so he decided to give the crystal to him. Kai received it from Kirou who was found in the rain, having been attacked by a gang. Kirou's memories were foggy, but he knew that the crystal was to go to Kai, so when Kai's mother (who is a doctor) left the room, he forced Kai to swallow it.