Arclath Delcastle was a noble in Suzail and the heir of House Delcastle. He was sometimes referred to derisively as the "Fragrant Flower of House Delcastle", owing to his family's penchant for floral designs in their mansion.
Arclath spent his free time visiting various private clubs, especially those that featured mask dancers. In 1479 DR, at the Dragonriders Club, he fell in love with a mask dancer named Amarune Whitewave, who was Elminster's great-(great?)-grandaughter.
In the days prior to King Foril's Dragon Council, Arclath and Amarune blundered around Suzail, slowly uncovering a plot by Manshoon and his flunky Marlin Stormserpent to destroy Elminster and seize the crown for Manshoon. Later, they helped Elminster restore the Simbul to sanity.
Arclath had a frosty relationship with his mother, who seemed more interested in being pleasured by young men than in the family business. His father was a drunkard who cared for little more than drink. Arclath and Amarune became lovers.
Initially, Arclath was extremely suspicious of Elminster, whom Amarune voluntarily allowed to possess her body. Later, Arclath came to trust the Sage of Shadowdale and even allowed Elminster's spirit to inhabit his body too.