(as) black as ink

1. Completely black; totally without light or color. The basement gives me the creeps, it's as black as ink down there! A: "I can't believe that Grandma's hair used to be black as ink." B: "Well, sure—you've only ever known her with gray hair." My hands were black as ink after working on that filthy engine all day.

2. Of a thoroughly evil, mean-spirited, or ungenerous mindset or disposition. She narrowed her eyes, and I could tell her thoughts had turned as black as ink. Whoever masterminded this heinous prank must be black as ink. Looking into his eyes, I saw his heart was as black as ink.