in uttarakhand, we consider chalawa a different kind of ghost. who sometime change its appearance nd some time come in animal form. but they didnt harm u, they only appear nd than disappear. although other state chalawa can be deadly.
chhal is like possession. when u visit jungle or smaller river or rivers, ghost can attach with u. sometime u didnt see it or feel it, or sometime u feel something weird (sound voice, wind blowing etc) or see ghost. possession can be two types (may be due to ghost type or its nature). first one is mild one. u can only get sick nd weak for long period. second one is dangerous one. in this victim do crying nd attacking, making weird voices, red eyes, laughing, get sick, harming itself or others, night walking nd sometime showing that ghost also. both possession can be dealt with special pooja or sacrifice of hen/cock or goat in that place, where that ghost attach with that person. expert chhal person, told by seeing effected person or ask that ghost by beating or with mantra, that who that ghost is nd where it attach with effected person.
infect every two or three year, we did jaagar nd ghateli pooja. in this pooja at night, they sing special pahadi songs of pooja. in which our kuldevi/kuldevta nd ancestors come in any person body. nd blessed everyone nd sometime told people problem nd their solution. than they leave after some time, when pooja (special songs) stops..u dont believe it, but i show it myself. they exactly tells what any family nd person facing problem. even i heard, sometime they runs on fire, but that didnt hurt them (when they r possession in kuldevi/kuldevta). they even remember, what happened that time.