|This article is about a/an transformation devices in Kamen Rider Kuuga.|
The Spirit Stones (霊石 Reiseki) are mysterious items that appeared in Kamen Rider Kuuga manga.
- Main article: Amadam
Any given successors can inherit the Amadam from the previous host if they are willing. However, the successor will suffer great pain and see illusions when merging with it.
- Main article: Alter Ring
If its host died, the Alter Ring is able to transplant itself automatically to the user's nearest relatives.