How about the following for a monster race, not necessarily for players. More like a BBEG.
Noktwar- Night Lords
The Noktwar are the basis of all myths regarding vampires and werewolves, but their true nature is known only to a few learned arcanists and travelers. They are immaterial beings, demons, who draw power from darkness but are damaged, even destroyed, by sunlight. In their natural form they are a sentient vapor, a dark mist that travels quickly across the land and sky. However, they rarely take this form relying instead on their consummate shapeshifting abilities. They can assume the physical form of any creature active at night though they prefer predators such as wolves, owls, bats, and panthers. In order to take human form, however, they must possess a host and only those who have committed the gravest of crimes are susceptible to their invasion. Robbers and murderers who haunt the shadows of cities are an easy target, but the Noktwar prefer bloody tyrants for they then can draw on the political power of such people to serve their own ends.
While inside a human host, the Noktwar is still vulnerable to sunlight, but less for flesh shields his spirit. Light weakens such a Night Lord, but can not destroy him. When in human form and not crippled by the sun, he can still shapeshift but he must warp the flesh of his human form to do so, resulting in monstrous beast hybrids which have given rise to the myths of lycanthropy. Unfortunately for the Noktwar it can only mimic, not create life so to survive in their host without it degenerating it must feed on the lifeblood of human beings. Typically the beast achieves this by altering the physiology of their host to attain the blood letting saliva and fangs of a vampire bat, though some more crude predators will merely devour their prey with mouths full of gnashing teeth.
A Noktwar is powerful, ruthless and cunning. It's human host is empowered by the spirit's demonic strength, quickened by its energy and illuminated by it's immortal and cunning intellect. Still the beasts can be destroyed. A beheading or burning can stop the demon and force him to flee his vessel but only sunlight can destroy him utterly which is why those few who hunt the Noktwar only pursue their quarry at daytime and why the Noktwar seek refuge underground, often in mausoleums, during this time. Their taking refuge in such places, along with the immortality of their host bodies, have given rise to the false belief that they are the risen dead. In reality, much of the psychology and evil of the host remains alive in the demon hybrid created upon his possession and the heart within his chest, though corrupted, continues its beat.
As a bonus if you accept this it effectively cockblocks all lame and overdone vampire werewolf stuff from polluting the RP. And you'll never have to see someone use the word Lycan as if they think every game with such monsters is set in the Underworld universe.