The last descendant of the Blackhalls, a famous (some say infamous) family of wealth in the history of Point Lookout, Obadiah is stubborn and is still entranced by an old book his family once lost. The Blackhall family was deeply involved in the commercialization of Point Lookout in the early 21st century. Constance Blackhall, head of the estate after the New Plague made her an unexpected widow in 2058, cooperated with entrepreneurs from the Isla Negra Realty Company, who had been trying to acquire family real estate unsuccessfully for years. Despite overwhelming local cultural resistance, Isla Negra persistently attempted to bring tourism and modernization to Point Lookout and St. Mary's County.
When Obadiah first meets the player, he is polite, and asks the player to sit down and chat. Obadiah sits in a wheel chair, next to a pair of gas canisters and crutches, signaling that he is disabled. It is here where you activate the quest "The Dark Heart of Blackhall" wherein you are requested by him to retrieve The Krivbeknih. However, once the player completes the Dark Heart of Blackhall quest, it is shown he is fully capable of walking.
Obadiah can be seen praying, in his basement, in front of a dead creeper, after completing the Dark Heart of Blackhall. The player is then given the option to engage in conversation after his initial disapproval and request that you leave his home. You are then given three unique choice options. When the player states he hides bodies in rivers, he responds by saying he and the player are more different than they can comprehend. Telling him that you thought that he was above "this occult nonsense" will cause him to tell you that you misunderstood and demean you. A third option will cause the player to tell him that you will leave and he tells you to make haste.
Living in the estate of his family, Blackhall Manor, he despises other inhabitants of Point Lookout to varying degrees, either because he considers them uncivilized or simply unintelligent and possibly because of the theft of the book. However, it seems he is aware of their belief of the powers of the book as well, and wants the power all to himself.
The gas canisters next to Blackhall's wheelchair are labeled "nitrous oxide" otherwise known as "laughing gas".
As mentioned above, Obadiah Blackhall sits in a wheelchair, suggesting he is disabled, but in reality, he can walk perfectly fine.
While in the basement, Obadiah may sometimes chant "Ug-Qualtoth is returned. Be afraid, worms." This same name is mentioned in the Dunwich Building terminal entries.
The Blackhall family is a reference to the Whateley family from the H.P. Lovecraft story The Dunwich Horror. This is shown as the player can alternately end the quest at the Dunwich Building's altar.
There are also similarities to the central family in The Lurker at the Threshold, a novel Lovecraft co-wrote with August Derleth, who published it after the former's death. As with there, an aristocratic man inherits his family's dark legacies.