Lacrimosa

Millenia ago, God acted as judge, jury, and executioner. He reigned with an iron fist over heaven and the mortal realm. Angels obeyed and bent to his will. One however, developed the courage to rebel against the authority that had held a fearsome grip on heaven. Lucifer Morningstar believed in a better version of heaven and the mortal realm. Such a world consisted of a democratic leadership, one where no one power had total control.
Lucifer gathered the angels in rebellion. God smote his own minions. Punishment for Lucifer was harsh and swift. God knew the most valuable thing to Lucifer was his betrothed, Lilith. Stripping him of the title of angel, God cast Lucifer to rule Hell. To further his torment, God banished Lilith to the mortal realm where her memories of Lucifer and their relationship were wiped away. Lilith was now mortal. He built a barrier between the three realms. Finally, God placed a seal on Lilith's neck. A simple golden cross. Should the cross be broken, the seal between the realms would perish and Lucifer would be able to enter the mortal realm.
The devil grieved his lost love. Building his empire beneath the Earth, out of sight of his tormentor. He amassed demons and hellhounds, waiting for the day he would be able to finish what he started and get revenge for the loss of his Lilith.