When Strahd was a mortal king of Barovia, he was in love with his brother's fiance. Her name was Tatyana. On the day that Tatyana and Strahd's brother, Sergei, were to wed, Strahd killed his brother. Distraught, Tatyana ended her own life. Since that time, seemingly to tortue Strahd in his undead eternity, Tatyana is reborn in slightly different forms. Always, she rejects Strahd's advances. Most recently, Tatyana was reborn as Ireena.
When the Wafflecrew travelled to Barovia's past, they convinced Tatyana that she was in danger. Simon killed her with a dart, but Evelyn was able to cast revivify on her. Tatyana and Sergei got in a carriage and fled the scene, with Strahd giving chase.  Strahd captured them and returned both Sergei and Tatyana to Castle Ravenloft.