The immortals are facing death.
After spending decades hunting for the famed relics of Merlin, locked inside his tomb, hidden to all living memory, the world ends. They all die, and then they return, in time and place, to his tomb. Only for death to come once more. And again, and again.
Now the immortals have to come to terms with dying, something they were promised to escape. But they also have to make one last choice, before their powers drained. To face the unknown, or continue to fight until their bodies give out.