On the outskirts of a small village stands a massive tree whose canopy disappears far above the clouds. While grandiose on the outside, its interior houses the humble Mortem Post, which receives and delivers letters from those who have passed on. Deciding to break protocol to lend a helping wing, Rain, a flighty little courier takes a skittish girl by the name of Mila on an adventure through the inner workings of the post office. Together, they search for a letter containing the last words of someone who seemingly never existed.

One part artbook, one part narrative! Taking place shortly after the events of the story, a courier by the name of Sulien makes land in the village of Vitae to chronicle the events surrounding Rain and her adventures through Mortem Post. Read journal entries and solve cipher-like puzzles in the artbook, then follow her adventure via new in-game scenes with point-and-click minigames to learn more about the world of the Cradle.

Mila has been taken under Neve's wing as a trainee in the Investigative department. When an old seaborn passes on, her last act spurs Neve to give Mila her first assignment as a proper courier: deliver each and every last letter she wrote.

A collection of tales following the lives of the different characters in Vitae.