Your knowledge is superior to mine in this area Dowrgi. I know that Equus is the name of a play by Anthony Shaeffer author of The Wicker Man about a boy who blinds horses; we get shades of that in the story of Branwen where Evynissiyen mutilates some horses in order to make them worthless, a quite graphic sequence just behind the child burning. Possibly Shaeffer was making some kind of indirect reference towards that particular story. Most gods and goddesses of the period which you mention were probably mentioned in inscriptions, this may be the only or main evidence of their existence or worship. The Romans did some interesting things with the Celtic gods. For example, Rosmerta was often depicted alongside Mercury, suggesting that Celtic and Roman beliefs were placed side by side. This occurred in Britain, not in Rome to my knowledge. Mars was I think involved in some way as well. I would very much like to see something on Rigantona explaining more of who she actually was.