A lot of theories have been posted regarding Verin's possible identity as a member of the Black Ajah. I won't revamp the facts here, although they are convincing. Rather, I'll go a step further to speculate that Verin is actually Mesanna in disguise. We know from CoS that Alviarin (please excuse spelling errors) thinks that Mesanna must be residing in the White Tower since she always appears in an "inhuman" manifestation, more telling evidence that she is in fact Verin can be seen in the prologue to LoC. In the meeting between Mesanna, Semihrage, and Demandred, Semi taunts Mesanna by telling her that she would make a good teacher. This apparently goes back to Mesanna's rejection as a researcher from some academy, presumable in the Age of Legends. What better place for Mesanna to make her lair in this age than in the role of a Brown sister, finally able to live out her desire to research aspects of the One Power. Additionally, when the subject of ter'angreal, angreal, and sa'angreal arises, all of the forsaken turn their eyes to Mesanna. She responds by describing in detail the precautions the Tower had taken to protect these objects. Had not Verin had somewhat limited access to this store as well? How else could she have given the ter'angreal to Egwene. Another small point prior to her interchange with Semi, Mesanna was playing with a tower of ivory domino's which eventually crumbled. I personally see that as a Jordanesque symbol for the broken White Tower in Tar Valon.