Medea
One of my favorite tragedies is "Medea" by Euripides. In it Medea, Jason's wife, a witch, is scorned when she discovers that Jason intends to marry another woman. Not being one to accept such things easily, she takes out her revenge on Jason by murdering their sons. At the end of the play she rides off on a chariot drawn by a dragon. (Being a witch she is capable of such things, of course.)
My attraction to the theme is just due to my fascination with the story. Medea seems to me to be one of the most wicked characters imaginable, and the play is one of those that is so violent that it challenges your perceptions of how dark and sinister those old plays could be.