Mortal Coils (The Mortal Coils Series)

Nothing exciting ever happened to fifteen-year-old orphans Eliot and Fiona, who are trapped in the strict, oppressive household of their grandmother. A chance visit, however, reveals that the twins are the offspring of a goddess and Lucifer, Prince of Darkness.

To settle the epic custody battle between these two families, the fallen angels create three diabolical temptations and the gods fashion three heroic trials to test Eliot and Fiona. The twins need to quickly learn how to use their budding supernatural abilities . . . for family allegiances are ever-shifting in the ancient, secret world they have entered, and only by sticking together will they be able to survive!