Spirit Shards

Spirit Shards are extremely rare crystals said to contain magic strong enough to absorb people's spirits, killing them in the process, but allowing them to live on in the crystal. Once a spirit shard has absorbed a spirit, anyone who uses it will absorb the spirit, completely and they will become the person who's spirit they have absorbed, but in their own body. To use a crystal, all one must do is smash it. If the crystal has no spirit in it, the person who smashes it will trap their own spirit. If the crystal has a spirit, the person who smashes it will become the person who's spirit is trapped, but in their own body. Once smashed to capture a spirit, a shard will immediately reform itself until it is broken again, then it will just smash normally and become unusable.

History
Spirit shards have existed since the beginning of recorded history, and are the rarest item in the known world. Only three exist in Dornrun, all three of them on display in the Serothi Castle.