If he happens to attack K12 on his first roll that might be the end of us. Which would be pretty funny.
Might be a bit tricky, but even then I think you'd have some clever ways to beat him.
There are a few different "first strike" effects now, (Owain, the Watchtower, Boars, Crimson Drum...) what takes precedence if opposing armies both claim first strike?
The general principle is the more specific rules supersede general rules. So in this case, the order should go, from first to last:
Crimson Drum (specific, artefact-based) -> The Watchtower (specific) -> Boars (unit effect) -> Owain (global effect)
Does that match with people's intuitions here? I'm prevaricating a bit on the last two, but my thinking is that boars are inherently more prone to charging than the barbarians.
What is the probability that he attacks the owner of a Marrowfat artefact? Which square does he attack in such a case, is this random? Does Owain join in these attacks in person?
It's an even probability (if there are 26 player-owned villages, and one Marrowfat artefact, he has a 1 in 27 chance of attacking it). Artefacts are held in the main castle unless explicitly assigned to a scout or marching army or set of defenders in another castle or fort. Owain marches with the army and will move from place to place each turn.
The Host of Prince Owain is not in the list of unique locations yet btw.
One moment...
I somewhat wonder if having the libraries are more of a danger then they are worth, they make the game a lot more interesting for sure, but they do seem to be popping out hard to deal with threats at a high rate. In this case, if I understand correctly, owain is going to be picking off a random village every turn, and making it a very dicey proposition to take them back, until basically we go conquer K4, which is, minimum, 4 turns away (and that'd be with A1 bombing for it as fast as possible and assuming no other threats popped up in the way)
Well, they raise both the power and danger level, as they seed many more artefacts into the world than would appear with normal tile generation. Most of the sites offer some sort of reward for beating them (even Owain does), but whether that balances out the danger they present is debatable.