The Meskellian is a renowned (and often quite mythologized) hangout for mercenaries and freelancers. It’s a mix of rough and tumble bar, secret society, interdimensional embassy, and mercenary agency. It’s a club, the current iteration of which has a distinct punk vibe to it. It’s very old, it drifts among the planes, and it changes management as the times change. Good pieces of literature to read to get into the mood and tone of this place are the Hellblazer and Rat Queens comics.
Its most unique feature is its status as a demiplane. Getting to it usually requires finding its physical exterior, but it is possible (however infinitesimally unlikely it might be) to stumble across a portal to it. Its long-time demiplane status (as most demiplanes are temporary) has given it some measure of self-sovereignty, making it ideal neutral ground.
Below and within the Meskellian are entrances to labyrinths, keeps, caverns, and the like. Places which contain treasure. Dungeons. Some of these dungeons are across the planes, some are physically connected to the Meskellian in whatever plane it’s on at the moment. Many of these entrances are freely passable and easy to find. Some are secret, and some even have conditions that need to be met by someone trying to pass through.
Sometimes the passkey for accessing a portal is a physical object, sometimes it’s a state of being, sometimes it’s an emotion, and sometimes it’s something that needs to have happened to you. The passkey can be pretty much anything and information on such passkeys can be quite valuable. These rules apply to nearly all magical portals in the multiverse, not just the Meskellian’s. They can be anywhere that has physical edges which can frame the portal; a doorway, a wardrobe, a chimney, or a loo. There’s no guarantee that a portal will remain after being passed through. Be ready to find your own way.
The regulars here at the Meskellian are a motley crew. In some ways, there is camaraderie among them but at the same time none of them really truly trust one another. When in the club proper, they don’t have to worry too much; the safety of all within is more or less certain. Out in the wild though, who knows.
Some regulars hold that there’s an unspoken bond among adventurers, that there’s a sacred trust. Some take a romantic view that this ancient establishment is the only thing standing between the darkest corners of the multiverse and the rest of the world. That the denizens of the club are a sort of knightly order. Others take a less grand view and just appreciate the company, being among comrades in arms. And there’s a sizeable number of folks here who think all of that is utter bunk. It’s a crash spot that offers food, drink, jobs, and access to dungeons full of treasure! What’s all this nonsense about ancient orders and honor?
The Archcouncil, temporarily formed by the formidable tyrants of the planes, seems to think that the Meskellian may hold the secret to repairing the damage done by the Paroxysm. The theory is that its planar wandering may be due to some unknown non-astral form of interplanar travel. For this reason, not only did the 60th Council of the Most Grave Crash at the Twain decide to grant over a thousand warrants of exploration, but nearly a third of them went to members of the Meskellian.