“All the lights in the gym’s basement flicker as black smoke emerges from the box. The three of them stare, wide-eyed, as it grows bigger and bigger, slowly beginning to take an unmistakably human shape: long arms, wide shoulders, face hidden behind dark shawls.”

» Vetalas are ghost-like beings from Hindu mythology.

» There are two types of Vetalas: ghosts ones, that can turn into smoke, and normal, corporal ones.

» Corporal Vetalas are tall, have dark grey skin, long claws and mouths full of rows of canines. They product venom that can put you to sleep or even kill, if the amount is right. The venom they produce is identical with the venom their ghost counterparts produce, that's why it's easy to recognize by smell. 

» Ghost vetalas are physically stronger than corporal vetalas. They produce the same kind of venom, but in contrast to normal vetalas, they're immortal. They can't be killed, but they can be trapped. Their bodies are made out of black smoke, and in this form, they can take any shape that they want - humanoid, animal-like, etc. Though stronger than corporal vetalas, they tend to be slower than them.  

» They're sensitive to silver. Silver weapons aimed at them make their bodies sizzle, and they lose strenght upon touching it. 

 APPEARANCES

» chapter eight of run a little faster

The last vetala they dealt with had a normal form, all bones and flesh and venom and canines; this one was different. This one is slower, but can deprive a grown werewolf of strength for a few long minutes with a single touch and even in its smoke-y form, it has incredible physical force, if the way it threw Baekhyun over the room earlier was any indicator.