The Last Goodbye — Amber R. Duell

500 years before Theo met Cassia, Leander met Lyda.

The Netherworld was never meant for the living. It steals a mortal's sanity piece-by-piece, day-by-day. No one understands that better than the God of Death. But the chance for even a single day of company is a seductive thing and Leander can't help looking forward to each sacrifice.

When the last mortal country outlaws human sacrifice, Leander's new bride becomes his last. Though he knows he should let Lyda continue on to her afterlife, the pair grows closer and the God of Death hesitates in the face of eternal solitude. But soon, Leander must decide between being selfish and selfless.