D-12-4 was a member of Mobile Task Force D-12 "Mud Slingers" who was killed during their team's expedition into SCP-1730.
SCP-1730 exploration[]
D-12-4 was dispatched alongside the rest of their team in front of SCP-1730's main entrance, and was the second to respond in the mic check conducted by D-12 Captain. After D-12-1 read the message "don't look at the walls" from the main lobby's wall, Four quipped that it was a little late for that then.
When MTF D-12 descended down a service elevator to Level B3, Four joined Cap in checking the rooms along the main corridor, taking the doors on the right side. Four discovered the black filth staining the walls, making note of its mud-like viscosity and metallic scent while taking a test tube sample. In one of the rooms, Four found the body of a man, half submerged in a pile of sludge. Checking the corpse for identification, Four found that the body's belt had a spot for a badge which was removed. Four followed Cap to backup One and Three, who were filling a snake-sized leech with lead.
As their team headed back for the elevator, Four confirmed for One that the left turn they were facing should have been a right. As Cap failed to receive any response from Two and Five, Four quipped about how everything was going downhill and was promptly told to shut up by their superior officer.
Following their team down the new hallway in search of a new way out of SCP-1730, D-12-4 stopped when D-12-1 found a door, locked shut and written on. As One convinced their captain to let them check the room, Four downplayed the finding as just another office door in a hall of offices. Standing behind One as they kicked down the door, the pyroclastic cognitohazard victim trapped in the room combusted, incinerating Four, One, and Cap.