Elixir (Covenant #3.5) by Jennifer L. Armentrout
Aiden St. Delphi will do anything to save Alex.
Even if it means doing the one thing he will never forgive himself for.
Even if it means making war against the gods.
Although I was a huge fan of JLA Ever Since I read Obsidian, this series was a little behind for me, but after Deity and Elixir I was amazed yet again by JLA's writing.