Spoiler Warning: Don't read the spoiler text unless you've read through The Gathering Storm in Robert Jordan & Brandon Sanderson's Wheel of Time series.

In The Gathering Storm we learn that Verin Mathwin is of the Black Ajah. She says that she had little choice in joining, after snooping into their business - but do we know what she has done for them throughout the course of the series or in her earlier career as an Aes Sedai.

I find it difficult to believe that she is just a "member" and hasn't performed any tasks for them, especially given her position with Rand et al. The Black Ajah don't strike me as the type to have wallflowers.