This background book is an Inquisition investigation into the diverse alien menace that threatens the Imperium. In a far-flung research station on Biegel 9, a renegade inquisitor has gathered together a collection of aliens from across the galaxy and is keeping them alive to study. When a rival inquisitor is sent to investigate his heretical menagerie, he uncovers many things best left undiscovered. With stunning background details on all the main alien races of the Warhammer 40,000 universe, and some new discoveries as well, it is full of amazing new artwork, including detailed dissections of the subjects investigated. Dark secrets are revealed, not only about the fascinating creatures under scrutiny, but also the working of the shadowy Ordo Xenos itself. This book is a must for any fans of aliens and the Warhammer 40,000.