THE UNKNOWN
The Unknown - Official Dead by Daylight Wiki

LORE SUMMARIZED

The lore of The Unknown is deliberately vague, presenting the killer as a mysterious, malevolent entity whose origins are debated. The lore explores several theories through the investigation of a graduate student named Olivia, including that it's a summoned demon, an alien, a government experiment gone wrong, or simply an urban legend. It thrives in darkness, mimics voices to lure victims, and is associated with a series of disappearances throughout history. Trying to uncover the unknown makes you it's target, and becomes a problem in missing people's cases due to the very nature of the creature.

PROMOTIONAL MATERIAL

What makes Unknown the most intresting killer, and one of my favorite characters in fiction, is the mystery that surrounds every detail of this creature. To promote the release of the "All Things Wicked" chapter, Behaviour released many teasers. The most notorius being the found footage of someone in a tent, being stalked and then attacked by the Unknown. Too fast to make out too well, and led to many theories. Then their was stuff like the security camera, where unknown crawls quickly toward the camera, but is too off screen to make out

I decided to take some screenshots from the new trailer to get a good look  at the upcoming killer : r/deadbydaylight I decided to take some screenshots from the new trailer to get a good look  at the upcoming killer : r/deadbydaylight All Things Wicked Official Teaser - Dead By Daylight Mobile

THEORIES

I know the entire gimmick is that looking into the Unknown is what makes it go after you, but I love this character too much to leave it alone.

UNKNOWNS IDENTITY

Probabably the biggest debate fans have when it comes to Unknown is what it is. So I'll cover a popular one that I personally believe, and add my own spin on it

The Unknown is the same kind of "species" as The Draunee/Dredge. In the Dredges lore we learn that the Draunee is a manifestation of all the cult members darkest thughts (read up on it, its deserves a movie or something). Now, look at what people theorize the Unknown is in the world of DbD. People theorize its a slasher, so it uses an axe and stands on two legs, people assume its an alien, it's able to shoot a UVX and contort it's body, and so on. So while Dredge is a manifestation of negative feelings, the Unknown is the manifestation of the fear of the Unknown. And to quote HP Lovecraft (who seems to have an influence on the unknowns design) "The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown". This would explain a lot about its Mori, and the reason the body completely vanishes. If the body is left behind you know the persons dead, but if theres no body, you get scared of what COULD have happened. You begin to fear the Unknown.