There's one event where a traveller or wayfarer comes to your castle, who looks like you. So when you agree to help him a demon army attacks your demesne. In three campaigns I have always lost to this army, because my hero was too weak or it was a second hero.
So this time I did turn back time after my second hero lost and put some strong guards on the demense. But the event never occured again.
Will this event reoccur on another shard? How can I save him? Is the only way to put very strong guards on the demesne as soon as possible? What is this event for anyway?

1. It can reoccur on another shard if you would use reversion after defeat.
2. You can save him by killing demons. I remember that my warrior usually could kill them
3. This event adds some interesting dialogs in astral on both defeat and victory.

Yes I had the defeat dialogues with Zarr and that other guy, would like to see the other ones! So about defeating them, does the event occur only if a hero is in the demesne? In that case I'd just keep the weak ones out of it, my main hero (a mage) could have won easily. Do province guards there help at all?

Thanks Grem, the next shard I trained my hero up and entered the castle after Turn 77 with him only, and 3 turns later it happened, so I finally beat them!

If a revision is used he will also reappear at the same shard but it seems that the %-chance is resettet or reduced.

After i noticed that he may appear twice i tested it 5 times and 2 times i had to wait 50-60 turns, 3 times 75-100 turns.