I see nothing concluant in
this article, mere interpretation rather.
Celts had sacrifices -POWS, criminals (Lindow man seems to have been a high rank guy, though) . I've heard of sacrificial shows such as the wicker mannequin.
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They are also said to have built funeral monuments where they exposed bones of killed warriors (Ribemont-sur-Ancre, France). See image below (try of reconstruction).
Very interesting people.