What does this Shakespear quote mean?

Question

"For I have sworn thee fair, and thought thee bright, who art as black as h**l, as dark as night. "

Is it about deceit?

Answer 1

I believe this is from sonnet 147 which speaks of a self destructive love.  If there is deception, it is the author who has been deceiving himself and who is now realizing that his love, whom he had viewed as fair and bright is actually evil and corrupt.

Answer 2

He was convinced that she was the perfect woman, and he agrees that she is beautiful externally; but later discovered that she wasn't beautiful internally... she was deceitful, evil, corrupt, and malevolent.

Answer 3

Unfortunately, he loved her as he thought her to be a good, caring and loving woman. However, over time, her actions proved that she was not pure of heart, but deceitful and evil.

Simply stated, she made him feel she was the woman for him.  Later he found out she wasn't all that.