Ghosts are the souls of deceased humans who are trapped on Earth unable to move on. Even angels can't interact with them and deliver ghosts to the afterlife, leaving their only option as resolving the guilt that is keeping them from moving on to Heaven.
After meeting Ella Lopez during a near-death experience, the Angel of Death Azrael claimed to be a ghost to her. For years afterwards, Azrael would continue to visit her friend in the guise of a ghost.
Throughout the Series
In "Boo Normal", Azrael, still posing as a ghost, visits Ella Lopez and helps her on a case. Ella later reveals to Lucifer that she sees ghosts and tells him about her friend Rae-Rae. However, Lucifer realizes who Rae-Rae actually is, having given his sister that nickname.
In "Yabba Dabba Do Me", Rory carries Dan Espinoza soul up from Hell to Earth, but he becomes trapped on Earth as a ghost, unable to physically interact with anything. Rory is amused by Dan's attempts to interact with the world around him while Dan is left frustrated and angry that Rory never told him what would happen to him.
In "Pin the Tail on the Daddy", Dan attempts to get anyone to see him with Dan the Frog appearing to be the only one capable of seeing him at first. Eventually, Maze and Amenadiel turn out to be able to see him as they are a demon and a angel respectively. Dan later asks Lucifer to return him to Hell, but Lucifer informs Dan that he's stuck since he became completely intangible once he crossed over to the mortal plane. As a result, not even angels can interact with him and Lucifer can't take Dan to Heaven or return his soul to Hell.
In "The Murder of Lucifer Morningstar", Lucifer brings Dan to Chloe whose powers from Amenadiel's necklace allow her to see him despite her being a mortal. When Lucifer returns Azrael's Blade to her in Heaven, Chloe loses her powers and becomes unable to see Dan again.
In "Save the Devil, Save the World", Maze attempts to help Dan discover the source of his guilt and release it which will allow his soul to ascend to Heaven. However, they are unable to figure it out.
In "Goodbye, Lucifer", Dan visits his killer Vincent Le Mec, believing that he holds the key to his moving on. After Vincent escapes from prison, Dan's attempts to stop him from killing a young man leads to Dan accidentally possessing Vincent's body. However, he is unable to get free and Lucifer doesn't know how to free his ghost either, suggesting that Dan will be freed when Vincent's body dies. After Lucifer suggests that he take advantage of the time that he has, Dan uses Vincent's body to visit his daughter Trixie and express his regret for not being the father that she deserves. Trixie reassures Dan that he was a great dad and expresses her love, pride and admiration towards him. Dan is finally able to let go of his guilt and his soul ascends into Heaven at last, leaving Vincent in control of his body once again.
In "Partners 'Til the End", Vincent reveals that he remembers everything that had happened while Dan's ghost was possessing him. He also reveals that Dan made it into Heaven.
Powers and Abilities
- Possession: Like demons, a ghost can possess a living human with some effort. However, it appears to be impossible to undo. Lucifer is unable to help Dan Espinoza break his possession, suggesting that his soul will be set free when his host's body dies and he can use the chance to enjoy life again. After Dan's soul is released by ascending into Heaven, Vincent Le Mec retains his memories of everything that Dan said and did while possessing him.
- Invisibility: Ghosts are invisible to everyone but angels and demons. Despite this, Dan the Frog was somehow able to notice Dan's ghost.
- Intangibility: Ghosts can walk through solid objects. Even angels are unable to touch a ghost despite one carrying Dan from Hell to Earth, with Lucifer explaining that Dan's soul became intangible even to him after he entered the mortal plane. As a result, Lucifer can neither return Dan to Hell or carry his soul to Heaven.