Herbert West was an a onetime alumni of Miskatonic University's Medical School, back in the early 20th Century. Following his graduation, West became obsessed with reanimating the dead. He began to conduct unethical experiments to achieve that end.
West acquires the Necronomicon
In 1908, West acquired one of the few surviving copies of the Necronomicon. He felt that the secrets within would help him create a formula that would be able to reanimate recently dead corpses.
Over time, West became a disciple of the Old Ones and vowed to free them from their empty dimension prison.
The Inner Circle becomes interested
In 1913, the Inner Circle, which was led by Jacob Carter (great-grandfather of Randolph Carter), approached West's friend and assistant, Dan Cain. They informed him that they were aware of what West was attempting to do. They asked Cain to watch West, and inform them when and if Cain felt that things were getting out of hand. Out of fear and concern for his friend, Cain agreed.
Things finally came to a head in 1921. West had built an altar room in the basement of his house in Arkham some two years previously. In that room, he had chanted strange incantations and had made sacrifices to the Old Ones. Until that point, the sacrifices had been animals only.
However, on that day, Cain went into the altar room and saw a boy that he immediately recognized as young Billy Clarke (future grandfather of Staci Clarke), who had been reported missing by his family the day before. West was standing over the boy, holding a dagger. When Cain asked what West was doing, West replied that animals were not enough to free the Old Ones, a human sacrifice would be required. Cain tried to convinced West to stop, but West would not listen.
Realizing that West was now lost to all that was rational or sane, Cain drew his revolver and shot West six times in the chest, killing him. With the help of the Inner Circle, Cain was able to reunite Billy Clarke with his family. The Inner Circle also sealed up the alter room, with West's body still inside.
Dan Cain then wrote a statement about what he did to West, which he gave to the Inner Circle for safekeeping. He died in 1973, taking the secret of what happened to Herbert West to the grave.
Rex and Hannah move into West's old house
Following West's disappearance, his house acquired a sinister reputation. It had many short stay owners over the following decades. When the county decided to have it torn down, the Arkham Historical Society got involved. They felt that such an old house should be preserved. The head of that society was also a prominent professor at Miskatonic University at the time. Said professor began to lobby the Miskatonic University to buy the house, which they finally agree to do in 1953. Most of the time it was used for storage and occasionally rented out for official functions.
As Halloween of 2015 approached, the ghost of Herbert West awoke, due to the continued presence of Rex and Hannah in the house. West guided Rex and Hannah to the sealed up basement altar room, where they discovered his skeletal remains. West then accused the Inner Circle of forcing Dan Cain to kill him.
When Rex and Hannah confronted Randolph Carter about this, he showed them Dan Cain's statement, in which they learned the truth. However, West refused to accept that what he had tried to do was wrong and vowed to prove himself right, no matter what. His ghost then vanished.
West's skeletal remains were buried by Rex and Hannah in the woods behind their house. Randolph explained that this was necessary to protect secrets the Inner Circle would not like to be exposed to the world.
West and Johanna Martense
West's ghost then travelled to the Catskill Mountains of New York State, where he met Johanna Martense. Johanna alone had survived Rex and Hannah's attempt to wipe out her degenerate family and vowed to keep trying to find a way to free the Old Ones.
After having been made corporal via a spell from Johanna's now destroyed copy of De Vermis Mysteriis, West then formed an alliance with Johanna to achieve that same goal, freeing the Old Ones.
Freeing of Hastur
In 2017, West and Johanna travelled to a South Pacific island, that Johanna had raised using her magic. This island contained the Old One called Hastur, who was resting in a state of suspended animation.
Despite the presence of Rex, Hannah, and Randolph Carter, Johanna and West managed to transport Hastur away from the island and succeeded in awakening him. Thus their goal of freeing the Old Ones is one step closer.
Rex and Hannah Chronicles Story No. 10: The Old Ones
Rex and Hannah Chronicles Story No. 34: New Frontiers
Rex and Hannah Chronicles No. 40: The Secret Of The House
Rex and Hannah Chronicles Story No. 46: The Island