More is unknown of the barghest then is known... The entity that fueled their entire creation is unknown, and remain hidden from the mightiest devils and angels. It seem to exist outside the natural order of things, just waiting to devour. Potentially from the outer realms? As mentioned- no one really knows...
Equally mysterious, but for more mundane reasons, are the rituals that enabled the barghests to ever come to be. Whatever records there were they were long lost or destroyed, by barghests (Not wanting others to suffer as they do) as well as those who sought to oppose them. Perhaps somewhere there is n old copy, or maybe someone could research the process again? What would happen then? One barghest is a serious force multiplier for it's allies, what if there are many?
And another question on the matter- is the goblin-wolf the only possible combination? Or can someone found a way to unite other races with other beasts? Can there be more "barghest like" demons?
And there is one more mystery, who the barghest experience all too painfully, and others probably don't even consider- How is it, to leave with Hunger, constantly inside you? Always desiring, pushing, insisting? How does it feel that for you to live, you must erase all shred of existence from others? How is it to feel the world hates you? The gods hate you? Thatyou have no place, neither on the material plane or another? And the cruel catch- that in order grow stronger, protect yourself, advance like others do, all that waits you is madness and death? Is it a wonder they hate everyone else, SOOOO much?
"Stalker in the woods":
We'll begin with a simple encounter- A native barghest looking for a kill, and perhaps teaching it's young whelps a thing or two about humanoids. The basic idea is to have the barghest as predator, gauging its prey strength (tracking skill, life sense), and then springing an ambush when needed. A stalkign wolf, only far more cunning and cruel, with some added magical powers. Barghests are consummate hunter. They would use the terrain, their animalistic gifts (Senses such as scent), their allies, their cunning and powers (Dimension leap, silent invisibility) to stalk the party, and prepare for the right time to ambush. It's powers can make it (and it's whelps) much harder to defeat...
Some aspects that could be emphasized:
- Treating the target as prey.
- Demonstrations to the whelps.
- Cunnin and unfairness- The barghest never plays fair, and would use every trick it has, and every vulnerability the PCs has (Or that it can create) against them.
- Potentially adding an ally that can benefit from the barghest powers (Goblin wolf rider, a worg, a lycanthrope). - The disturbing Dark Influence making the PCs "evil" (Paladins and priests of good deities may find this especially disturbing).
As the party makes attacks against some goblin settlement, one of them summons the barghest. (Not by magic, but by mundane means, such as using a hunting horn). Once the barghest arrives, the party might mistaken it for just another goblin (Potentially a caster?) or wolf, yet it quickly becomes apparent that there is more than meets the eye.
The emphasis here is working with the goblin population, not on it's own. Cunning and ruthless as it might be (not necessarily though), it now acts with the groups interests at heart. The barghest would mostly use it's group powers, and superior fighting skills. If possible, emphasize that this "newcomer" works on their behalf as part of some agreement.
A strategic tool:
The barghest is a magnificent strategic tool- it weakens it's enemies and improves it's allies simultaneously, it can infiltrate and spy on most places, it can almost never be tracked, and if it has a fresh supplies of animals and such, it can be powered to be effective nearly always! The barghest is a fine ally to an unscrupulous person. The barghest adheres to the deals made with it, and can be quite a versatile asset. Hey, it's mere existence strikes terror in those he fights against! Who wants to die like that!
This little paragraph just came to show the possible uses of a Barghest to any force, especially a military like force. Use it well, but don't forget it follows a strict deal!
A deal with the (odd kind of) devil:
Due to some urging matter, the party may seek (or may be approached) a barghest, for information, power, capabilities and more. They'll have to strike down a deal with it.
The emphasis here is about making the deal, and the barghest's peculiar way of deal making. (See above)
"Can you make me a better offer?"
A particular barghest worign for another group is giving the party, their allies or such a very tough time. The party is sent/ goes on their own to either dispose of it, or turn it to their side. The barghest might be interested, but the deal needs to be significantly better, and it must not hurt the current deal. Loopholes and "legal" interpretations might ensue. This might be a very difficult mission for "goody" adventurers, but might fit in a "choose the lesser evil" type of scenario.
The emphasis here is to find how to make a deal when another one is in place allready (Which the barghest won't violate).
"Ongoing business relations":
This might follow in the footsteps of the two previous ideas- after dealing with the barghest once, and having been treated fairly, an opportunity presents itself again (the barghest tries to make it look accidental almost, perhaps using its connections and other debts to do so). The characters may have the opportunity to deal with it, and again the deal is fair (You could even let the player think it's a resource, almost like a cohort/ follower/ NPC they trade with on regular basis).
But then, some dealings later, the barghest makes another fairly odd request, still appearing non-threatening. Only this time, as the party tries to fulfill it's part of the deal, they find that they cannot agree to the consequences of their actions. Suddenly it all becomes complicated- either they comply with the deal, or they have a hungry barghest, with the power of a debt stone one their heels...
Emphasis- deal with the characters fairly until the critical moment (The best liars tell the truth all the time, until it matters). Make the barghest demand they fulfill their end (if it's still possible), and make the re precautions known, at least vaguely, before they refuse. Otherwise, it will come collecting!
"Assassins' ace in the hole":
A barghest is also hired/ called in order to act in an assassination. The party may learn of the fact fairly late, and suddenly they are looking for an evil outsider other than just an assassin. The barghest may be fitted with the best gear, mundane and magical to succeed at it's job, so identifying it may not busy easy. It might make matters difficult if there are a few of the fiends... Note: Dealings with barghests is dangerous, and not common place. So almost always, the target is a very important one...
"FINISH HIM!": Barghests add a special horror to groups who rely on ressurection magic- once you go barghes, you DON'T come back! If the party uses these tactics sparely, their enemies might get a "finisher" just to make sure the adventuring pests "stay down!".
"The path of Hunger, a path of power & desperation:": Someone the group really values- a cohort, an old character a player left out, an allu or anyone else they care for, have somehow stumbled upon the secrets of turning into a barghest. And for it's own reasons, it uncovered the ritual, and went on with it, turnign into a barghest. Yet after a short while, they realize their mistake, and their existence strains them, threatening to turn them mad!
it calls upon the party for help, and they may try to find ways to reverse the process ,while the person is driven by Hunger, and may complicate everything. At some point, it may even decide it has to get through the process or die trying! Can the party stop it? Should they? Can they? At what cost?
You could easily make a similar process for non goblin-wolves pairs.
The emphasis here is dual: Experiencing the road and transformation of the barghest, and the moral dillema of it's continued existence, on the expanse of others.
"I'm back! nd I'm better than ever!"
An enemy goes through the process, after having been beaten once. It becomes a recurring villain, with the growth of the barghest making him on par (or more?) with the PCs as they level..
Finding the debtbone!
Someone made a bad deal. (Either the PC, an allied NPC, or such). The barghest can't be persuaded to break the deal, so the only way (That avoid getting it on your tail) is to find the debt bone and destroy it. Most debt bones are kept by the barghest themselves though, so this may not be that easy...