I hope we get druids for the Celtic religion in a DLC/free expansion later on. It's quite interesting that the autocephalous Orthodox of CK II would be a really good representation, as there was e.g. a main druid for Gaul and all druids could "excommunicate" a person for misbehaviour. An excommuinicated person was no longer able to participate in religious practices and was also marked as impure, i.e. no one wanted to be around them.