From the introduction:
It is recorded that in the Year of Settlement 241 a Grievous of the Oera'dim was first encountered by Humankind. Up until that time such a creature had been unknown to Men and it fell to the fate of a Cartographer of the Deep Guild named Iirdor Halbek to be the first to witness such a Being. Little is known of how a Grievous might be brought into the world but it is rumoured that the Hordim torture and defile one of their own to the point of madness, reducing it to a primal state of aggression and ruthless malice. Such creatures are used to guard the Hordes' most valued treasures and it proved only by chance that the transportation of one such Grievous led to the meeting that is the subject of this adventure. It is known that Halbek had mounted a mapping expedition into the borders of the Lower Coldarai, and in the foothills of those mountains came into contact with a Hresh scouting party. Pursued into the hills with only a weapon and satchel of food in hand he tried in vain to escape his pursuers, but found instead the edge of a deep ravine and a deadly plunge into its dark interior. Your adventure begins as you fall, your pursuers hot upon your trail. To survive you must find your way out of the ravine before you are caught by the Hordim. That is your mission.