Ah, the temple is the key to some useful undeads.
The Holy Site, like I said, was only saying it provided one water gem (pool of something or another), with no additional text.
The province was in my very own dominion, and a pretty strong at that, and I was hit whenever I stationed some undead troops there... I still am, come to that.
Well, maybe a bug, then.
Unless a site has hidden from my acashic record...