These are russian folk characters before christianity, sort of nature spirits.=)
"Chert" or "bes". Actually he has lots of names. Evil minded troublemaker, lived around human enviroment - family problem, illnesses, cattles diseases, murrain and much more - all blamed on him. In later christian concept has been merged down with a satan.
"Leshij" - forrest spirit, usually unfriendly to mankind, if run into human could makes him lost in the woods or lead him in a swamp.
"Borovik" - pine tree forrest spirit, most of the time quiet loyal to men, if they behaive respectively - do not litter or hurt trees for no reason. Otherwise does the same as above. Helping peasants find mushrooms by moving around from one spawn to another and whistling.