Phoebe Peters was Urian's wife until Stryker made everyone believe that he had murdered her because Urian had betrayed him by helping Phoebe's pregnant sister Cassandra and Wulf Tryggvason escape. Stryker wanted to kill Cassandra in order to end Apollo's Apollite bloodline, thus killing Apollo.
Urian later found out that Phoebe was alive but had been driven insane by the souls she used to extend her life. To spare Urian the truth, Stryker had been keeping her prisoner ever since he found her slaughtering the Apollite village where Urian and Phoebe had lived.
Phoebe asked Urian for a divorce because she wanted to be free without anyone telling her what to do.