Outwardly, Mortimer was an elderly adventurer who supplied magic items to the Bazaar of Nabulee el Jasafir. Secretly, however, he was a powerful blood mage from the Orient who arrived in Waterdeep with the objective of opening a portal into the Shadowlands, and thus corrupting the entirety of the city. It was later also discovered that he was in a temporary alliance with the Margasters, that provided him with various human test subjects in return for him giving the Margasters’ his most prized creation: the Greater Flesh Golem
This flesh golem he gave the Margaster Family was used to infiltrate the Order of the Golden Lion as an assistant to High Supervisor Aelfred.
Sometime in 1486 DR, the Margasters ordered Mortimer to frame Nabulee el Jasafir with the murder of Archibald’s son Aaron. He managed to achieve this through the use of spells that modified memory, the use of flesh golems imitating Nabulee el Jasafir to incriminate him and by planting a deadly item on the auction front that was sold to Aaron.
Eventually, the Seekers traced their investigation to Mortimer and confronted him in his lair with the assistance from an old friend of Korosu named Hiroyashi. Mortimer became extremely powerful thanks to absorbing the corrupting power of blood magic, but he was eventually killed by the group with some help from Hiroyashi and Sir Victorum, who arrived in the middle of the battle.