The Callisto Catacombs Guardians of the Galactic Sentinel Book 3

The purpose of the ancient, enigmatic Deimos Artifact has been discovered - the small, tetrahedron-shaped construct is Humanity's key to access the giant Galactic Sentinel Network...Activation of their Sentinel signaling device presents Mankind with an unprecedented opportunity - an invitation to join the Grand Amalgamation of Galactic Civilizations, an interstellar organization representing over five-hundred different intelligent species...Citizenship requirements are simple: Humanity needs to establish a peaceful relationship with their closest galactic neighbors, the Hordea, a peculiar race of intelligent plants...And they have to put a stop to the endless internal wars which have plagued the species since inception...The downside? Failure to achieve citizenship places Mankind at the mercy of the Custodians, a brutal and ruthless Amalgamation archrival, who've already enslaved over a hundred "undesirable" species...Attempting to fulfil the Amalgamation's membership requirements, Zack, Ariane, and the rest of the Deimos expedition must voyage to the far reaches of Human space, including a perilous foray down to the surface of the ravaged and lawless planet Earth itself...Opposing them at every step are the Custodians who, with the assistance of greedy, traitorous Humans, are covertly doing all in their power to ensure Humanity's bid for citizenship will end in failure...In the meantime, there is compelling evidence that another ancient artifact awaits discovery...