Fear Dimension

"I don't understand how, but it seems that this dimension can take our deepest fears and it can manifest them physically."

- Leo Fitz

The Fear Dimension is a dimension in the Multiverse which manifests the fears of those exposed to it. After a rift in space-time occurred at the Lighthouse, the Fear Dimension spawned illusions to haunt the S.H.I.E.L.D. team. The tear into the dimension was eventually closed with compressed Gravitonium.

Explosion at the Lighthouse
"I think that when the Monoliths exploded, they tore open something that I can only describe as a Fear Dimension."

- Leo Fitz

A rift in space-time was created due to an explosion that destroyed together a White Monolith, a Grey Monolith, and a Black Monolith. The explosion created a connection between the Fear Dimension and the Earthly Plane.

Violent Illusions
"So, Kree Warrior. Check." "And if that is Lash, double check." "What about that forest on Level 27? " "You mean an overwhelming collection of branchy things with birds and bugs and the floor all covered in worms? Are you kidding? That's a horror show." "Okay, triple check."

- Daisy Johnson, Melinda May, Phil Coulson and Deke Shaw

Multiple illusions were generated by the Fear Dimension by tapping into the mind of the S.H.I.E.L.D. agents who were hiding in the Lighthouse. Lash destroyed D.W.A.R.F.s sent by Leo Fitz to investigate the explosion of the Monoliths, enabling Fitz to figure out the nature of the spacetime rift. Deke Shaw's ignorance of the real life on Earth and fear of insects created a gigantic forest while Daisy Johnson's fears manifested in the form of a Kree Warrior who attacked her and Shaw.

Closing the Rift
"I was hoping there was enough Gravitonium with some modifications to create a perpetual force that can stitch together the tear in spacetime."

- Leo Fitz

In an attempt to shut down the Fear Dimension, Leo Fitz created a Gravity Containment Device out of Deke Shaw's Gravity Puck. Phil Coulson chose to be the one to take the device to the rift, where its activation would close the tear in spacetime. However, once arrived, Coulson encountered an illusion of Mike Peterson, who tried to convince Coulson that everything he had lived, from the creation of his team to the events in 2091, were made up by his brain while he was being resurrected. Peterson's illusion attempted to take Coulson to the rift and almost succeeded before Coulson stated that he did not believe him. As the illusion was destroyed by the real Deathlok coming to aid Coulson, other illusions generated by the Fear Dimension attacked them: Lash, Hive and Vrellnexians. However, all the illusions were destroyed and Coulson activated the Gravity Containment Device, which temporarily shut down the Fear Dimension. Nevertheless, Fitz was aware that the device they used was not powerful enough to completely close the rift, which kept generating illusions from time to time. As such, an illusion of Deke Shaw's mother was created, only to be destroyed by a Kree Warrior in front of Shaw himself. Shaw then destroyed the illusion of the Kree Warrior. Only when S.H.I.E.L.D. brought back Gravitonium from the Principia did they get a chance to permanently close the Fear Dimension, which once again created an illusion of Hive in his astronaut form. Fitz struggled to find a way to compress the Gravitonium and insert it into a new Gravity Containment Device. This led to the release of his dark personality from the Framework, The Doctor, who took control and captured Daisy Johnson, removing her Inhuman Control Device and restoring her powers. With it, Johnson successfully compressed the Gravitonium and took the new Gravity Containment Device to the rift, where both the devices combined and sealed the Fear Dimension.

Trivia

 * Despite not having an specific parallel, the fear dimension seems to mash the Halls of Fear and the Dimension of Dreams, also knwon as the Nightmare Realm.