The Scaredboards are Nightmares introduced in Episode 3. They are the first Nightmares to be introduced in the series, and are essentially the most stable. These Nightmares seem to have an official name, but they are nicknamed Scaredboards as their true name is unknown and they are all in the forms of cardboard cutouts.
With the exception of N0ra#4, the Scaredboards cannot speak the same way Dreamythicals do. They seem to communicate with each other psychically, unable to talk to Dalsie or any of the other Mythicals.
The Scaredboards usually resemble Mythicals, like G'joob and Yawstrich, with some visual differences. The only way they can move around is if they are on something mobile like a utility cart, hence why the main Scaredboards are always seen atop of one. It also seems that the Scaredboards try to take advantage of other Dreamscape creatures to help them move around.
Episode 3
In episode 3, the Scaredboards are introduced when they suddenly appear as Dalsie is attempting to escape the Matrix Halls. Starting with 4010, the Scaredboards simply chase Dalsie down the halls, knowing they cannot properly communicate with her.