Desmond, nicknamed Dez by John Constantine, is a barkeep in New Orleans. There he met Constantine and the two formed a relationship. He later broke up with John after being freed from Neron due to being sent to Hell.
In 2018, Desmond met John Constantine at the bar where he worked and the two soon formed a relationship.
Sometime after, hunted by a powerful demon Neron, Constantine asked Desmond to leave town for his protection. Hearing about the danger John was in, Dez gave him his Medallion, which was imbued with a protection spell, before agreeing to Constantine's plan. However, Desmond didn't leave and instead made a deal to bind his soul to Neron's in exchange of the demon sparing John's life. Constantine found out about it when in an attempt to send Neron to Hell, he had to send Dez there as well. 
Hearing about Dez's fate, Laveau pressured Constantine to save "the last of [her] line" and he returned to the night they met with Charlie and had her prevent the two from meeting.
However, Desmond and John now met a few days later, leading to the assumption that their meeting is a fixed point in time, meaning they were supposed to meet and this event can't be changed.
Constantine then decided to travel back and break up with Desmond before he could fall for John, lying to Dez that he simply used a love spell on him and what they had wasn't real. initially, Desmond understood the situation as John trying to sabotage his own happiness and tried to talk him out of it, but at the end he left after claiming what they had was real, which caused the whole timeline to change.
original timeline restored and freed from Neron
John at first tried to time jump multiple times in hopes of creating a timeline where Desmond wouldn't be sent to hell and also the legends to continue to hunt down magical creatures without killing them. However every timeline he created with charlie only made the legends much worse than the last time. Eventually he gave up and realized he had to restore the timeline to as it once was. He then erased Desmond's memories so he could continue his relationship with John until the point in time came when he would be banished to hell. Neon would use Desmond as a vessel until both Nora and John found a way to separate Neron from Desmond freeing his soul and body from the demon. While trying to ask for a ride in the Time Bureau he meet up with John who tried to rekindle their relationship. However Desmond refused do to the fact that John banished him to hell. When John stated that he could erase his memories of his time in hell Desmond refused stating its something were both going to live with he then broke up with John and left.
Powers and abilities
- Bond with Neron: Desmond bound his soul to Neron's in order for John to send him to Hell. However, in an attempt to kill Neron, John and Nora managed to exorcise the demon from Desmond. Neron subsequently latched onto Ray Palmer as a result.
- Medallion: Desmond used to possess a medallion of the saint Marron, the patron saint of runaway slaves, which he later gave to John Constantine. The medallion is imbued with a protection spell and has been in his family for generations, once belonging to his great-great-grandmother, Marie Laveau.
DC's Legends of Tomorrow