CRGreathouse
Community Supporter
Epametheus said:First, the blackguard needs to prove himself. He can either fetch some rare delicacy for it (like a silver dragon egg -- or wyrmling), or he can prove to it that he can beat the crap out of it in single combat. If the former, he may well start a vicious cycle of getting bossed around by the thing. If the latter, it'll probably just hate him more than usual, but grudgingly serve (after all, if it pushes it luck, it might have to worry about something like getting dim-anchored and then killed). Regardless, he needs to prove to the thing that it'd either (a) greatly benefit from working with him, or (b) is going to suffer if it screws with him. Quite possibly both.
Assuming they can get it to work with them, the nightmare should demand it's own share of treasure, including magic items. Note that Nightmares don't keep treasure. It simply eats its share.
It also demand special "food" regularly -- probably a sentient being tortured in a specific manner. Willingly working with this thing should probably damn the rider beyond all redemption. Edit: oh, they already are? Keeping a carnivorous horse satisfied probably wouldn't be that hard. Unless you want the give the Nightmare some requirements that are more "out there" (maybe it has a fetish for unicorns? that'd be a pain in the arse to accomodate).
Nightmares normally can't communicate, but since this is some sort of cool unique nightmare, go ahead and give it the ability. Hell, just give it Tongues or something like it. Having it always address people in their native language, no matter what it is, could be a little freaky.
I like this! Eating its own share of treasure... that's just too evil.

As far as evil beyond redemption... yeah, I think they are. It's bad enough that we've had problems between group members killing off information sources -- for no reason -- before asking questions. (Think Weird Al's "Trigger Happy".) We've had our first PC kill last game.
I'll have to think about the language. I have so many possibilities! Yours would certainly be eerie, and surely the easiest on me.