One of the most shocking stories ever to be written in comics. Deathstroke the Terminator has a long held grudge against the Titans relating to the death of his son Grant Wilson the original Ravager.
In order to fulfill this grudge he seduces a 15 year old with the extraordinary ability to command the very earth to her will.
Terra successfully fools the other titans into accepting her onto the team as Terra, even stealing Beast Boy's heart in the process, but when the time comes to execute Deathstroke's final plan, Terra proves too emotionally unstable and literally brings the house down killing herself in the process.
The Titans were never entirely clear what happened to them and Terra's betrayal was considered an aberration despite the fact that she clearly relished her role as a sexpot and a traitor.