Raavastas are a race of fiends with distant demonic ancestry indigenous to the World Axis cosmology of 4th edition Dungeons & Dragons. Introduced in the 4e version of the Manual of the Planes, raavastas are adept shapeshifters and manipulators who are rarely seen in their true forms; humanoid jackals and foxes. They are fairly "traditional" fiends, in that they are consummate dealmakers who love to ensnare mortals and other races in webs of deceit, deception and diversion, all for the singular goal of amusing themselves through the pulling of strings. Though that's not to say that they don't enjoy indulging their copious appetites for classical hedonism in the process!
Dealers, bargainers and merchants, raavastas can be found throughout the Abyss and the Elemental Chaos for the most part, but readily go wherever they can find potential victims. The Feywild, the Shadowfell, the mortal world; they have even been known to inveigle their way into the Astral Sea, where they can barter and match wits with angels, devils and gods. Thanks to their twin powers to shapeshift and to master any tongue with but a few moments of study, they can fit in wherever they please, and they particularly enjoy stalking the streets of Sigil.
Gathering magical rituals and trinkets like a honeypot gathers flies, raavastas are adept mages, at least when it comes to protecting their own hides. They will not hesitate to use stockpiled talismans to thwart attempted meddlers, nor to escape if things seem to be going sour. Add to it the incredibly diverse array of creatures that can be charged with bodyguarding a raavasta, from humanoids to bladelings to tieflings to magically-bound genies and demons, picking a fight with a raavasta definitely shouldn't be your first choice.
On the meta-level, raavastas were created to reinvent the concept of the Arcanoloth, a species of yugoloth that no longer had a place in the 4e cosmology due to the redundancies of its heavily alignment-based purpose and the dialing back of the Blood War. Amusingly, this was actually worked into the raavasta's lore; the species are believed by planar sages to descend from the Arcanoloths, a species of bestial, shapeshifting, conniving, hedonistic demons who were such assholes that the Demon Princes chased them out of the Abyss in irritation! The Arcanoloths, or so it's believed, went on to mutate and evolve into two new strains of fiend; the raavastas, and the rakshasas. If this is true, neither of the "sibling" races is willing to claim the other as kinsfolk.
The most famous of all raavastas is Shemeshka the Marauder, who is mentioned in the Dungeon Master's Guide 2, statted in the Demonomicon, and has her own Demonomicon of Iggwilv article in Dungeon Magazine #205.