I happened upon a book called Soul Retrieval by Sandra Ingerman at a magical store called Second and Charles. I have been interested in Soul Retrieval for a long time but didnt even know where to get started with it, so this book is quite a gem.
It turns out that a lot of the implements to perform a soul retrieval were part of the ancient celts repertoire.
The bodhran is a perfect example. It is very similar to the drums that cultures that practiced soul retrieval used.
The druids also had a medicine [crane] bag, where they could have stored items used for the soul retrieval ritual.
They would have had guardians and helpful spirits to aid them on their journeys.
The only thing I have never heard of the celts having is a soul catcher, but crystals can be used for that as well.
Im curious about nonordinary reality and the shamans that use ecstasy to reach it.