Brother Adrian first appeared trying to stop the Warehouse Agents from using Ferdinand Magellan's Astrolabe because it would create an evil. However, he failed to do so and was in fact killed by Pete, but not before he told Artie that it would create "an evil that will live with you the rest of your days."
Brother Adrian later visited Artie to inform him that the Astrolabe had been used and requested Artie's assistance in finding and reversing the effects of the artifact. He also gave Artie his number to call him in case he needed to contact him. Artie called him later and spoke with him; there, Brother Adrian told him that the Astrolabe was responsible for the Reign of Terror.
Adrian later discovered that it was Artie who activated the Astrolabe and claimed he'd do whatever was necessary in order to make Artie undo the evil he'd created. As a warning, Adrian, or another member of the Brotherhood of the Black Diamond, broke into the Warehouse and stole Bobby Fischer's Bag of Marbles and left a black diamond in their place. The marbles were found again at Hugo Miller's house. This was Adrian's way of saying "use the astrolabe to undo what you have done or we will destroy your life's work" to Artie.
In order to further destroy Artie's life's work, Adrian stole several artifacts from the Warehouse, including Primo Levi's Scarf, the McCoy Rifle, Vincent Van Gogh's Stormy Night, Mata Hari's Stockings, and the Honjo Masamune. The thing that all these artifacts had in common was that they were all collected by Artie. With help from Steve, Artie was able to find and retrieve these artifacts.
Adrian later stole Lewis Carroll's Mirror, donating it to a thrift store along with a camera flasher with a tag on it that said "Click Me". A woman working at the thrift store used the flasher and Alice took over the woman's body. Alice claimed Adrian had hired her as an assassin to kill Vanessa Calder, Artie's girlfriend, in order to get Artie to use the Astrolabe. However, Adrian's plan failed and Alice was imprisoned back in the mirror (or at least a piece of it) before she could kill anyone.
Following the debacle with the Mirror, it was learned that Adrian had stolen Harriet Tubman's Thimble from the Warehouse, but Claudia was able to find where Adrian was hiding so she, Artie, and Steve could get it back. While on the pursuit for Adrian, it was discovered that Adrian was using the Threshold of Limentinus to break into the Warehouse. Adrian was able to escape with the thimble, but Artie was able to get the Threshold from him so he couldn't use it to break into the Warehouse anymore. However, Adrian claimed that he had other artifacts he could use.
It was later revealed that the Brother Adrian Artie saw was just a side effect of using the Astrolabe. The real Brother Adrian and the rest of the Brotherhood of the Black Diamond were imprisoned in Rembrandt van Rijn's Painting Frame. Brother Adrian had never been to South Dakota, never even met Artie before; Artie was just imagining Brother Adrian threatening the Warehouse, its agents, and their families when in actuality Artie himself had done it. The Brother Adrian that Artie had been seeing was been nothing more than a hallucination, created from the downside of using the Astrolabe.
The real Brother Adrian, once up to date on the events, tried to help them restore Artie to sanity, and stop his plan on spreading Sweating Sickness using the Chinese Orchid, however he angrily demanded that when all the trouble was over, the Astrolabe would be returned to him and the Brotherhood.
- The name "Adrian" has a Latin origin, and means "Man from Hadria; dark one." Hadria is a town in northern Italy, named for the Adriatic Sea, which is itself named for its dark-colored sand. His name is quite likely a reference to his role as the personification of Artie's evil side under the influence of Magellan's Astrolabe.