This is a slightly more technical post oriented on using a shadowbeast in combat. For shadowbeasts in general, look here.
A shadowbeast has three main abilities: Shadow Tendrils, Blistering Shadows, and Quaking Fear.
Shadow Tendrils are extensions of the shadowbeast itself, and are effectively it's limbs. It can manifest 3 of these at any one time, and can use them to hit, grab, trip, or anything else that a tentacle is capable of.
Blistering Shadows: A denizen of the darkest hell, shadowbeasts grapple and swarm over their damned prey, their very essence burning through flesh until nothing remains but stains on the ground. Any flesh (or non-metal object) that touches a shadowbeast is burnt as if by powerful acid. Without quick action, entire limbs can be lost to the corrosive effect of this vicious effect.
Quaking Fear: Deep down, almost all creatures have a fear of night and darkness. In the darkness, you cannot see that which is sneaking up on you, or that which lies in wait for you to cross it's path. The depths of night are when the darkest of creatures come and stalk their victims. Merely a sidestep away from living shadow, a shadowbeast is so close to night incarnate that it gives off a radiantly cold aura of fear that can cause all but the strongest to freeze in quaking, primal impotence. Such a target is easy prey for it's assault.
Shadowbeasts are cunning, silent predators. There is no roar of anger, no growl of warning, no hiss of subtle threat. Your only warning is the utter darkness of shifting shadows, slowly creeping into the circle of your torchlight, and the slowly growing sense of utter terror building in your chest.
A shadowbeast, as with almost all predators, prefers sneak-attacks on it's prey. It will hide in the shadows, waiting until the perfect opportunity to swarm over and engulf an unwary victim, muffling the screams of torment with it's body as it maliciously rends it's prey apart. When confronted with a group, it will slowly pick off stragglers, dragging them off into the darkness one by one.
The one true defense against a shadowbeast is a preponderance of light. Born of darkness, light will sear and burn it, but only the strongest and brightest of lights will actively turn one away once it has begun it's attack.