Adam

Adam was a human that came to the Devildom in search of his lost love. However, at some point he died and became a spirit that was residing in a tombstone at a cemetery near the mausoleum of the Devildom's past kings. It is unclear how he died or when he died as the year of death on his tombstone was too faded to read.

Story
Note: this section may include spoilers

Main Story
In Lesson 8-13 (of Obey Me! Nightbringer!), MC went with the demon brothers (excluding Lucifer) to a cemetery near the mausoleum of the past demon kings to help Mammon with a ghost-busting job he accepted. All of the tombstones had inscriptions that were written in the ancient language of the Devildom, but MC noticed that one tomb had an inscription that was written in the human language. Some of the inscription was faded, but she was able to read the name "Adam" and the phrase "I'm waiting for you". All of a sudden, a bolt of lightning struck.

In Lesson 8-16, a spirit named Adam had possessed Mammon's body. He tells them that he is a human and has been waiting so long for MC to appear. Adam says that he came to the Devildom in search of his lost love. But, he became lost in the darkness as the Devildom wasn't a place meant for humans. Adam ended up wandering around for a long time. For a while, he was unable to see or hear anything until he heard the sound of a trumpet one day. He thought it was creepy, but he also felt a sense of relief after finally hearing some kind of noise after so long. After the trumpet stopped playing, Nightbringer appeared in front of him. Adam cried while begging Nightbringer to help him find his lost love, but Nightbringer replied that he was unable to do anything for Adam right now. But, he promised that there would be a person who would one day appear and be able to help him. Nightbringer then offered to bring Adam to the place where he would one day meet the person who could help him and Adam accepted his offer. He also told Adam that this person would possess the ring of light which could open the gates of the Celestial Realm. This would help him reunite with his lost love. He then asks MC to take out the ring of light in their possession which MC does.

In Lesson 8-18, the demon brothers don't believe that MC, or any demon, would be able to open the gates of the Celestial Realm (since they for some reason believe MC is a demon). This makes Adam despair as he wonders if he waited all this time for nothing. But, MC says there is is one thing they can try. Adam tells MC to try it as he doesn't care how risky it is. MC uses a teleportation spell in order to send Adam to the Celestial Realm. They are able to accomplish that by using the power of the ring of light which also absorbed some of the demon brothers' powers (excluding Lucifer's). This was despite MC's pacts with the demon brothers being weaker after being transported to the past. As Adam was being transported, he told MC that Nightbringer left a message with him for MC stating that it wasn't time for her to return just yet.