It is the day of coming of age for Adam, Prince of Mo. Adam is to succeed his father in a time of uncertainty. The blood-thirsty warlord Moorkus Rex, leader of the Tyrann, is burning a warpath across the world.
After meeting the dinosaur adviser, Dina, Adam agrees to an audience with Dina's dying grandfather, Tao. Tao tells of Adam's great-grandfather "The Architect" who, with his dinosaur companion, Graa, united dinosaurs and man against the Tyrann. Together, they built citadels throughout the world, allowing humans and dinosaurs to push the Tyrann back. However, "The Architect's" son, and Adam's grandfather, "The Enslaver", destroyed all the citadels except for Mo. Driving a wedge between the trust of dinosaur and man, and allowing the Tryann to return.
Adam returns to his father, King Gregor, to confront him on his desire to rebuild the citadels. The King, reluctant to lose his only son and heir, initially refuses. Realizing that allowing the Tyrann to continue unopposed would only increase their power, he gives his blessing.
Adam must travel the world forging alliances or all will be lost to the might of Moorkus Rex and the Tyrann.
As a post-Myst adventure game, Lost Eden borrows much of its interface design from the franchise. The game takes place from a first-person perspective. Backgrounds are pre-rendered 3D while characters are 2D animation based off Jean-Jacques Chaubin's paintings. The interface is navigated by a cursor that automatically changes to the correct action when hovering over the environment. Occasionally, players have to solve puzzles by dragging-and-dropping items from their inventory (at the bottom of the screen) to relevant areas on the screen.