I only recently started playing Wild Mana, so apologies if this was previously reported.
In a recent game (version 8.34) where I was playing as the Luchuirp, one of my cities revolted because the support from one of the Noble Houses (Ghallanda, I think) fell too low. The new city was also Luchuirp, led by the Traders(?) of Erebus. One of their starting units was Barnaxus! I had already built Barnaxus and he was still alive. I'm sure this can't be intended.
I don't know if this happens with other civs' heroes (or religious heroes, for that matter), since I haven't played enough games of Wild Mana. (Also, I've gotten better at maintaining the support of the noble houses, so I haven't had cities revolt since then.)
To round this out, I immediately declared war and recaptured the city, killing the other Barnaxus and capturing the Pieces of Barnaxus. The good thing from a game balance point of view is that I was not able to use the Pieces to build a second Barnaxus of my own.
Anyway, just wanted to report this.