Unlike Lady Lily, whose legend is tied to 14th-century nobility, Blackjack has no verified historical backstory. Instead, his nickname was "affectionately coined by the castle staff" to describe the identity behind a decades-long series of bizarre, recurring pranks.

While Lady Lily is typically seen gliding silently through corridors, Blackjack interacts directly with guests' physical belongings.

• Guests frequently report unpacking their bags only to find their items have been rearranged or hidden in strange places around their hotel rooms. 
• He is particularly active in the dining and bar areas, where he is blamed for sliding glasses off tables and knocking cutlery onto the floor. 
• He has a slightly louder, more disruptive side that includes slamming heavy doors in the middle of the night.

Blackjack’s antics—combined with the castle's other spirits—gained global media attention when Lumley Castle hosted international cricket teams: 

• In 2000, members of the West Indies Cricket Team were so intensely spooked by paranormal disturbances that three players checked out of the hotel all together in the middle of the night. 
• In 2005, during the famous Ashes tour, Australian all-rounder Shane Watson became so terrified by unexplained activity in his room that he famously left his room to sleep on the floor of teammate Brett Lee’s room. 

While terrifying to visiting athletes, the castle staff generally view Blackjack as an innocent, albeit frustrating, prankster rather than a malicious entity.