Covenant Lands & Invasion

This would make an interesting adventure for players! But maybe you are asking because it all happen in the background, and your own players are in another covenant and you want to describe to them what happened to Blackthorn after the invasion ?

In any case, I assume Blackthorn would like to maintain status quo (no change in mundain relations). This will need time and ressouces, though, even for an autumn covenant.

But whatever the means, I think an automn covenant should be able to acheive this, otherwise it may be their covenant's winter.

If you want to play it out with your players, you could pick any suggestions in this topic, things your players like. I personnaly like Vetrenius' idea the most.

My idea would be along the line of Blackthorn knowing well in advance of the invasion (having spies following key personnalities): there is no "surprise" invasion of a large land. An autumn covenant, if having enough interest in mundain affairs (as is the case now: you said they posses land and ressouces) ought to have already diplomat, spies and the like in surrounding lords courts.

When a lord invade another's domain, they are in search of ally or at least neutral people from that land. I don't see why mundain nobles would not want to negociate with the nice people Blachthorn already sent to them! Otherwise, it means Blachthorn really want to battle that mundain invading army (!?)

If they can't negociate with the Normans to spare most of their belongings (lands, ressources, etc), I would suspect some other influence that is trying to make sure Blackthorn suffer from such an invasion.

If their is some other "influence group", ennemy of Blackthorn, this is where the real battle occur, and it won't be infringing on hermetic laws, because this other influence will probably be supernatural in nature (depending on your saga) or anyways comes from people actively trying to hurt their covenant (and the code allows for covenants to defend themself).

Well, if you intend to go for an active approach, you can always ponder the damage an invisible magus with a reasonable Perdo score can do, wandering about the camp and spoiling all the food just enough to cause food poisoning. Likewise, PeAu for causing a cloud of bad air to waft over the camp. Or Re(Co/Me/Vi) depending on your choice for summoning a Spirit of Dysentry or Cholera.

Or you could steal an AC to the lord in question, and use ReMe effects to make him ignore or be friendly towards the covenant. Yes, it'll warp him but combining medium term cooercian with actual diplomacy, gradually shifting the emphasis from one to the other, should solve your problem.

If you're particularly bastardly and have the relevent Mysteries, you could always kill the lord and then bind him into his own, preserved corpse to act as your pawn. You'd need to have him die elsewhere after a few years or people would really start to notice, but it's doable.

If you're feeling cruel and have a local regio, you can also lure outriders and eventually anyone you want into said regio and then use illusions to bar the exit, leaving them lost and trapped. Give them a month, and you can have someone from your covenant rescue them, earning their gratitude and giving you bargaining power.

I suppose you could always just get a load of soldiers, load them up with spells to boost their combat prowess and send them berserk into the camp to have more or less mundane men slaughter the invading army's leaders, thus effectively causing them more problems than you're worth.

Since, however, the setting assumes that people do at least know of the existence of the Order, it might be best merely to point out quietly to the invader that you're sworn to neutrality as long as you're left unmolested (get a priest to witness this if you like), state quite clearly the privilges you currently enjoy and point out that in the event that his men get too enthusiastic with your grog's daughters, you're quite prepared to ensure that his crotch rots, and he develops the palsy, thus scuppering his chances of conceiving an heir. Should he already have an heir, the same penalties can always be side-shifted.

Thank you all for your thoughts... very helpful for my saga.

As Iudicium suggests, this is a background event in my saga, though I do have ideas centering around the PC magi being asked by the Normans to help negotiate a peace with Blackthorn.

I find myself quite partial to the idea of magical harressment and raiding on the part of Blackthorn... very Welsh.

We'll see how it plays out.