ominous
A sign of something unpleasant that's about to happen; inauspicious
conundrum
Riddle; mystery
morose
depressed
altruistic
Unselfish; caring
exuberant
Uncontrollably joyous
opaque
Too dark or thick for light to pass through
concur
To agree
impede
Get in the way; hinder
pompous
Filled with self-importance; arrogant; obnoxiously proud