Updated.
You seem to have some thoughts on the flavor, so do you care to write up something?
Not really, but I can whip something up...
A humanoid figure with glistening skin like seamless black leather. Its face is as smooth and featureless as a pool of oil. Strange ridges run across its limbs, skull, and torso, almost breaking through its skin.
The buseni are fearsome-looking outsiders that guard many of the routes to the second layer of Arcadia. A busen's default form is the jet-black humanoid described above, but they have malleable bodies which take on whatever shape best suits their mission. A busen patrolling a broad mountain pass might be a slavering wolf-thing, one guarding a sinkhole down to a tunnel could be a sucker-pawed crawler with enormous bat-like ears. Buseni have no bones, their skeletons are odd ridges that are just barely restrained from projecting through their skin. A busen can jut a pair of these ridges out from its flesh and use these protrusions as weapons.
In their normal duties, buseni wait in some dark spot until someone tries to pass them without permission. They then suddenly step into view and display their weapon-protrusions. Buseni do their utmost to kill any intruder who reacts to this warning display by attacking. If intruders try to parley, the buseni telepathically interrogate them as to their purpose in trying to enter Arcadia, then demand the intruder remove all their possessions (including weapons, clothes, and even jewelery) while the buseni examine them. The buseni then use Sense Motive to determine their trustworthiness, only allowing creatures to pass if they assess them to be non-evil.
The buseni are lawful creatures with no tolerance of evil, who would sooner die than allow an evil creature pass by on their watch. Their function as sentries is obvious, and they obey orders assigning them to specific guard missions, but who (or what) does the ordering is unknown. The origins of buseni are equally mysterious, since they do not appear to be formed from petitioners or breed like normal creatures. Some sages believe they are spawned from the plane of Arcadia itself.
A busen's malleable form generally remains around 6 feet in length or height. It weighs around 200 pounds.
Buseni communicate telepathically.
They could form a mouth and speak, but their regular missions give them no cause to. Buseni are fully familiar with the Abyssal, Celestial, Draconic and Infernal languages.
