Specimen 3 is a dark brown spider/centipede-like creature with a hard, shiny exoskeleton. Its body has four distinct segments, with each sporting a pair of legs. Specimen 3's front-most segment has eight round greenish eyes and bears five sets of pincers.
Specimen 3 appears for the first time after the player reads the Generic Lab Assistant's note. The Assistant claims to have heard a clicking noise before he died. After reading the note, and moving towards the exit, a clicking noise is heard, and Specimen 3 enters the room and chases the player. It deals about 30 damage on contact.
During the chase, Specimen 3 creates holes in the ceiling, from which it may drop down. It crawls instead of floating, and moves at the same speed of Specimen 2.
It takes about 4-8 seconds for Specimen 3 to drop down from one of the holes in the ceiling to chase after the player.
Hitting Specimen 3 with the Axe will stun it for a few seconds.
According to the CAT-DOS, it was in testing before it escaped and killed the Generic Lab Assistant.
"WRITHING SNEEZES", Specimen 3's chase theme.
Sounds heard when Specimen 3 is near the player.
- Specimen 3 is inspired by the game Resident Evil.
- In the lab that Specimen 3 broke out of, there are four creatures still contained. These are believed to be subjects 1-4.
- At one point, there was a bug where Specimen 3 would get stuck in the floor. This appears to have been fixed.
- Specimen 3 is referred to in notes written by the generic lab assistant as "Subject 5" which has caused many people to be confused as to which specimen the lab assistant was talking about.
- In update 2.3, once the player died from Specimen 3, the game would crash.
- Specimen 3 doesn't have a death screen.
- Specimen 3's body is segmented, similar to the old Specimen 10.
Differences from the original game:
- It is much faster.
- Crawls out of the hole on the roof just after the player passes under one.
- In rooms without a visible roof (bridge rooms), it enters through the door.
- Can pass through Specimen 1.
- Upon dealing damage to the player, crawls away, does a circle, then resumes crawling after them.