The Host, previously referred to as The Author, is one of the characters Mark played in a two part collaboration with Cyndago called Danger in Fiction. He served as the primary antagonist and the narrator of the story, compelling the members of Cyndago to do his bidding simply by writing their future actions on a piece of paper. For a long time, the Host had been treated as one of Darkiplier's many personas until reappearing much later as a separate character alongside Darkiplier in "Markiplier TV".
In Danger in Fiction, the Host has no notable features and is simply presented as Mark in his regular clothing. A photo from an unused sketch shows the character as having a bloody cloth wrapped around his eyes, suggesting he has been blinded. In "Markiplier TV", this became a part of his standard look.
The Host, known as the Author at the time, guides an unwilling Daniel with only his voice through a remote building housing two unidentified hostile creatures. After several disputes with the Narrator, one of them resulting in throwing away a character ID card made for him, Daniel is forced to go through an unidentified doorway, which results in him being ambushed by the Host before waking up in his bedroom. After calming down, Ryan gives him back the same ID card he discarded in his supposed dream, much to Daniel's shock.
After finding out that Daniel, now a patient in a mental hospital, had escaped, Ryan receives an anonymous notebook, later revealed to have been sent from the Author, that transports him to a forest where he needs to collect pages scattered throughout the woods in Slender Man fashion to progress further into the story, all while being stalked by the Author. Upon collecting the final page of the Narrator's story, Ryan is ambushed and knocked out by the aforementioned person with a baseball bat. Shortly after, a restrained Ryan wakes up in a shack and is greeted by the Author who reveals his abilities to manipulate others through writing and demands for him to cooperate in order for the Author to create another best-seller. As he monologues, Daniel shows up and shoots the Author in the back, releasing Ryan and leaving the wounded man alone in the cabin.
The Host is apart of the table of judges deciding whether or not to air Wilford's new project "Markiplier TV". Of the seven egos there, he is one of the two that do not express dislike for the project, choosing instead to narrate what's happening. In the end, Markiplier TV is never aired.