Sentient creatures from an ancient past, the Rakshasa are a dangerous race with powerful mutagenic powers.
Their origin is long-lost, as is their memory, even if many says they're somewhat related to the treacherous Loki. Their name only appears in some ancient documents and stories, so for the most they're considered an old myth.
This is most due to the fact that the last Rakshasas had been trapped in Cocitus's glaciers for centuries, condemned to eternal imprisonment.
Recently, some rumors are spread that they managed to evade from their prison, most likely have been released. It's unlikely that Cerberus would let any of his prisoners escape, but something may have helped them. Whatever the truth is, the Rakshasas are most likely free, and their infiltration already spred Gods knows how.
Rakshasas are a reptile-looking species with bluish skin and various horns and spikes along their form. Their true form vaguely rensembles a 2-meters tall humanoid structure. The Rakshasas can crawl on walls, move on both hind and four limbs, and breath cryogenic energy.
Though bestial-looking, they're not low in intelligence, and understimating them is a fatal error. In fact, Rakshasas are actually smart and intelligent enought to be compared to dragons, even if an eventual family bond is unlikely. They can use objects and weapons, most of the time stealing them, and also magic, even if it is mostly the king that uses spells.
Though Rakshasas look reptilian, they have an insect-like attitude: they live in what they call "hives", and their society is divided in castes: a king, and the servants. The king is the only Rakshasa with a complete free will, all the others being sentient and smart, but still inevitably bonded to the hive's and the king's sake.
Rakshasas have a life cyrcle both fascinating and scary: with their cryogenic breath, they capture and harvest prey in a special room the hive homes, the ice preventing the body from rotting and consume, then they bring it to the king. The king unfreeze the prey and swallows it. Once done, it gains the complete genetic map of that creature, as well as its memories, and will lay an egg within minutes. This egg contains that same genetic code, fused with Rakshasa DNA. The egg will hatch within hours, revealing a hatchling Rakshasa who grows to its full size and power within minutes.
This hatchling has already the intelligence that characterizes its species, plus a little special ability guaranteed by this life-style: it can shapeshift, to be the exact copy of whatever creature its incorporated DNA belonged to. Also, since also the brain of the victim has been analyzed, all the toughts and memories are assimilated and becomes part of the new Rakshasa. A Rakshasa has three forms: its true one, the acqired form, and a hybrid between the two, wo combine all the genetic abilities inherited from Rakshasa and host alike. They can shift freely between the three. The hybrid is usually the one used to fight, adding numerous and various abilities to the Rakshasas's armies.
The Rakshasa king is a powerful engine of destruction itself, as big as a dragon, and armed with great strenght, ice breath, great intelligence and genetic manipulation. The king, much like its spawn, can shapeshift, but into every single creature it vored. That's, altogether with its cleverness, what makes a Rakshasa king very difcult to individuate. It also possess elastic jaws and stomach that allow it to swallow even large creatures. Even if the king needs only a few genetic material to make what it has to, it's endless gluttony makes it enjoy its meals completely.
Despite their quite animalistic looks and behaviors, the Rakshasas are a race that likes to act noble, and are very greedy. Their kings are usually found disguised acting like nobles or rich merchants, enjoying mundane life while taking a break from laying eggs. Usually, they use their mansion as hive, and they always have a hidden room magically refrigerated to harvest their future generations. These bodies can lay there for very long, for richness is like a drug that keeps the Rakshasas busy.
Rakshasas kings use their acts also like a mean to get new victims, turning their employees into their spawn one by one. The spawned Rakshasas are completely sentient, and they work hard to act as the people they're supposed to impersonate. However they're, like their king, extremely greedy and hungry for money and power, and will get it with every mean necessary, even if they bow to their monarch's every wish.
The noble Rakshasas are quite calm right now, content to drown in richness, but a new arrival could change this; another race has broke free from Cocitus, and they do not like that...
There, the newly-adaped Xeno-Zillas, now made into the demonic race: the Rakshasa. I know many of you knew them as feline-like, but you know what? Nobody knows. Feline Rakshasas are D&D's creation. Nobody knows their true form, so...I improvised XD