sombreness in WordNet English dictionary

1. a feeling of melancholy apprehension
   gloom  gloominess  somberness  sombreness 
   
2. a state of partial or total darkness
   "he struck a match to dispel the gloom"
   gloom  somberness  sombreness 
   
3. a manner that is serious and solemn
   graveness  gravity  sobriety  soberness  somberness  sombreness