dark cloud

cloud nine

Often in the phrase on cloud nine: a state of bliss, elation or happiness.

cloud seven

Often in the phrase on cloud seven: a state of bliss, elation or happiness.

dark horse

Someone who possesses talents or favorable characteristics that are not known or expected by others.

look on the dark side

To examine a situation, usually unfavorable, from a negative perspective; to be pessimistic or miserable.

oh dark hundred

Some unspecified hour in the early morning (implies an unpleasant time to be awake)

oh dark thirty

Some unspecified hour in the early morning (implying an unpleasant time to be awake).

see the dark side of the moon

To do or experience something exceedingly difficult or rare.

shot in the dark

A guess, attempt, or choice made with little or no evidence or knowledge.