Yet so they mourn, becoming of their woe, That every tongue says beauty should look so. (Sonnet 127)
In Sonnet 127, the speaker introduces the dark lady by saying that standards of beauty have changed, and now having a dark complexion is in style. He says that one would not consider sorrowful eyes beautiful, but in fact, anyone would want eyes as beautiful as hers. The speaker makes clear in this sonnet that even though the dark lady may not be conventionally attractive, he still finds her beautiful when she expresses her true feelings.
Therefore I lie with her, and she with me, And in our faults by lies we flattered be. (Sonnet 138)
Throughout Sonnet 138, the speaker explains how he and the dark lady continue to lie to each other—perhaps both physically and verbally—even though they know such behavior is wrong. However, he says that pretending to trust each other feels easier than facing and expressing the truth. Earlier in the sonnet, the speaker admits he’s lied about his age. Yet he indicates that he suspects a more serious wrongdoing on her part, suggesting her secretive and untrustworthy nature.
Or, if it do, not from those lips of thine, That have profaned their scarlet ornaments And sealed false bonds of love as oft as mine[.] (Sonnet 142)
Here, in Sonnet 142, the speaker tells the dark lady not to scold him, especially from lips that have been used to cheat on him. Readers may note that in this sonnet, the speaker also admits that he too has had many affairs. These details reveal the toxicity and dysfunction of their relationship. Yet, despite all of the infidelity, the speaker remains in love with her.
For I have sworn thee fair and thought thee bright, Who art as black as hell, as dark as night. (Sonnet 147)
In Sonnet 147, the speaker describes how his love for the dark lady has driven him mad, to the point where he feels ill. He says he must have been insane to have ever described her as beautiful and radiant. Although their relationship started out with him praising her unique, dark beauty, her evil nature now charges those characteristics with connotations of hell and night.