Disclaimer: Let me say at the outset, I do not have Realms of Power: Infernal, nor can I get it before my next session, nor do I want anyone to quote large (or even small) sections of it, in violation of copyright.
Anyway, I have put myself in a sticky situation in my saga. My magi have run afoul of a Norman knight who happens to be allied with Infernal powers. Unfortunately, I'm really not sure what to do with the fellow. I've run ArsM for a goodly while (mostly 4th ed) but the Infernal has never played a role in my sagas. I find now that I'm not really sure how to deal with it.
So I have this evil knight. He a dark, sadistic, vicious, oily, generally unpleasent fellow. There is nothing darkly romantic, glamorous or seductive about him. He is definately aligned with the Powers of Darkness.
Question one: What does that do for him? Should he have some sort of supernatural power? Obviously, I can do anything I want, it's my saga, but I'm just not sure..
Question two: If I do give him some kind of power, what kind of thing should it be? I've already decided, he isn't the charming, seductive, corrupting evil. He's the violent, sadistic, cruel evil.
Not sure how to handle the infernal might thing, BUT have you considered the possibility that he is actually just a bad guy with the Blatant Gift that just went undiscovered by the magi "around" him while he was growing up? Give him a supernatural ability or two and folks might think that he's Infernal but really he's magical and the infernal has just been coaching him along.
Give him an infernal might and then devise one or two powers using hermetic magic guidelines, then divide spell level by 5 for magical might points used. Add a brimstone stench when powers are involked.
While RoP:I helps with infernal characters, it's not critical. Just use the ArM core rules for creating creatures with Might for the below, and you should be fine.
What I'd suggest, because this is how I think, is that the knight himself is mundane, but he has committed himself to evil, and for that reason, he gets demonic "luck" for his destruction and to keep him from harm. If his demons can be neutralized - or mundanes can survive his depredations - he can be killed. He's just very hard to kill and does grotesque damage.
Demons often are invisible in Medieval Europe. So, in my view, traveling with this evil knight are many demons, medium-size and small. They are PeIm invisible but not really "hiding" their presence as much as non-corporeal, so a InVi or Second Sight would reveal a horrific host around this knight of impossible twisted creatures, some as small as a gnat and others as big as a brown bear. Non-magi seeing this host probably would have to roll a personality check against Bravery to avoid being struck dumb or panicked with fear.
Here's some of what the demonic host does:
Some demons cause fear in people and animals (treat as CrMe or appropriate level). This is often paralyzing, incapacitating fear, so the knight can destroy them. Also, since their fear overrides their faith in Divine salvation, the knight's killing them will likely send them to Hell.
Some demons are destroyers of wood, stone, and metal (PeHe or PeTe as appropriate). The knight's weapons seem to cleave through all armor, doors, and occasionally even a stone wall (with a power like Obliteration of the Metallic Barrier). Opponents who strike at him may find their weapons blunted or shattered before they touch the knight.
At least one demon may cause a wound to be unhealable without significant magic (PeCo at 30+). The knight must inflict the wound first, but then it is cursed; it will never get better normally (although it may worsen, and then won't get better from the worse state) without a significant CrCo ritual or Divine intervention (holy power or miracle).
Another demon may, once per day, blot out the sun or moon and render the area around the knight a temporary infernal aura of level 3-5. This power lasts as long as the demon concentrates or until two diameters, whichever comes first. Some other demon will allow the knight to see in this darkness, but others may not be able to - eyes of the cat will be minimally helpful as there will be little to no light.
If the knight is seriously injured but not killed, and escapes, there will be a demon who seeks out the one most beloved to the person or persons who injured the knight and will transfer the knight's wounds to him or her. This can be prevented if precautions are taken or the demon destroyed before it strikes.
The demons will interpose themselves between the magi and the knight; they will grant the knight some infernal magical resistance.
Depending on how long-running an antagonist the knight is, he can have companions in evil (thus making him an army), the ability to teleport home, or an alliance with someone like Frederick II who may not like him but feels he's necessary to continue his wars, so outright killing the knight will embroil the covenant in a minor part of a larger, unrelated war.
He is a knight, and also a psychotic arsehole. What would he sell his soul for?
How about he made a pact with some entity of hell along the following lines
"Never shall you be pierced with sword, spear or arrow, nor crushed by mace, flail or stave, clubs, hammers and stones shall have no effect on you and knives, axes and cudgels shall turn aside."
In return he swore to kill at least one true innocent a month, in such a fashion as to cause others to doubt the goodness of god.
i.e. in return for virtual indestructibility, he messes up a lot of lives and leads people away from god. Say by killing children, exposing the inability of other lords to protect their peasants, etc...
This of course has the added side effect that like all good devil bargains, he is still vulnerable to something or other, just find a weapon that isn't on the list and hey presto that can kill him. Give him some magic resistance from resident demons so that the magi have to find out about his original deal so that they can find the weapon that CAN kill him. Of course he'll find out they are snooping around and come for them, it'll be great fun.
