Two ships, carrying scientists from different generations, arrive on the first habitable exoplanet. The discovery of a now-extinct, ancient race thrusts them together on a mission that, if they fail, will mean the destruction of Earth and Salacia.

Cora, one of the last Sentinels, remains the last line of defense against an unknown enemy laying siege to her planet. Together with a handful of allies, Cora must find a way to protect the one thing this enemy had come to destroy - the humans.