I had an interesting problem happen in my current game. The Umber did a simultanous attack on several of my resources. I defended a couple and lost one. After dealing with the army, I rebuilt the mine.
A couple turns later the AI did the same attack on different resources. He actually got me a little off guard and destroyed two of my three shards, and I mean destroyed the shards. I could not rebuild the shrines. The actual shard crystal itself disappeared from the entire game.
Are the shards themselves supposed to get destroyed? If so, I will definitely be posting guards next to those from now on.