Chernobog in Slavic mythology can literally be translated to The "Black God." He is the God of the night, chaos, evil, Hell, evil luck and infernal darkness.

His complete opposite is Belobog (The White God).

You might remember this feller from Modest Mussorgsky's A Night on Bald Mountain in Disney's Fantasia.

Also transliterated as Chernabog, Czernobog, Tchernobog.