Specimen 7 appears to be a large, moving, red-and-black wall of distorted images that resemble skeletons and corpses.
Upon entering the door, the player sees themself in a flesh-like hallway. After exiting this hallway, Specimen 7 will start chasing them. From that point on, the player must run through a series of twisted corridors with shifting images along the walls, created by the player's mind under the influence of Specimen 7.
Though slow, Specimen 7 kills the player instantly on contact.
CAT-DOS states that it is "only effective on subjects with a past trauma or mental issues".
"STRANGE WIGGLES", Specimen 7's chase theme.
- Rarely, Specimen 7 can turn into a normal wall.
- Sometimes, the Rooms which Specimen 7 "corrupted" can be very glitchy (e.g. transparent walls).
- Rarely, other Specimens may appear alongside Specimen 7 during the chase.
- The Cat's relation to Specimen 7 is unknown; for some time, the cat was suspected to be Specimen 7 itself, and may indeed be a part or a consequence of its existence, sort of like a psychic Good Cop/Bad Cop.
- Specimen 7 is visually similar to Giygas's final form from Earthbound (or Mother 2) while its behavior may be a reference to a similar mind-world flesh wall chase from Penumbra: Black Plague.
- In the 2.5 update, the player no longer stays in Room 410 for the duration of the chase: it now progresses.
- Specimen 7 doesn't have a death screen, along with Specimen 3.
- Specimen 7 can be encountered one time only, along with Specimen 13.
- It is one of three specimens that can instantly kill the player on contact, the others being Specimen 9 and Specimen 12 while in the Mansion.
- The art for Specimen 7 is recycled from another project Akuma Kira was working on.
- Bizarrely, it seems other Specimen can spawn and begin to chase the player in the Flesh Hallway right before Specimen 7 spawns, meaning that, if one is 'lucky' enough, they can be chased by two Specimen at the same time, as shown in the gallery.
- Specimen 7, along with Specimen 13, are the only two specimens from the original game not found in Endless Mode.
- Specimen 7 may also be a reference to the Wall of Flesh, from the popular action-adventure sandbox game, Terraria.
Unlike the original game, the specimen is 10 degrees inclined
The rooms during the chase became a bit darker than the original game