A former Margaster Family spy, who, at some point, signed the contract to the Extradimensional Mansion.
Ulrach was once an ambitious illusionist when he managed to discover and utilize the powerful artifact known as the Tome of Absence, which managed to greatly enhance his illusions at a terrible cost - the slow disintegration of his very soul.
Upon realizing the nature of his affliction, Ulrach grew desperate to find a cure. The Margasters soon learned of his condition and approached him with an offer — they would dedicate their resources to researching a cure. In exchange, Ulrach would remain in Waterdeep and use the Tome of Absence to create perfect spies: creatures of pure illusion, loyal to the Margasters.
As part of this arrangement, Ulrach took residence in the abandoned mansion of the late noble Albrecht Sparrowing, where one of his illusionary creations assumed the guise of the noble’s grandson.
Over the years, Ulrach became increasingly disillusioned with the Margasters’ empty promises of a cure. Worse, he discovered that he could no longer leave the mansion. His illusionary spies continued to serve him, but their allegiance to the Margasters grew stronger than their loyalty to their creator. They began concealing their clandestine missions from him, though they still provided him with valuable intelligence gathered from across Waterdeep.
In 1486 DR, Ulrach’s creations presented him with a contract granting access to an Extradimensional Mansion. Unaware that they had stolen it from the Seekers — and that they had been ordered by the Margasters to eliminate that very group — Ulrach accepted the offer and relocated to the mansion.
When the Seekers arrived to eliminate the spies of the Margasters, Ulrach offered to form an alliance with the group after they murdered all of his creations. Ulrach offered hidden intel on important figures of Waterdeep and promised to testify against the Margasters. In return, the party would spare him and attempt to find a cure for his condition.
As of now, without the Seekers attempting to find a cure, the Tome of Absence has presumably disintegrated the rest of his soul, assuming that he hasn’t found one himself.