EDIT: nvm i just had to shoot at it until it died
EDIT 2: by "it" i mean the severed head of john romero, the cyberdemon is still FUCK
A merchant crosses your path -
"I've got nothing, I tell ya."
use the Doom2 iwad, heres a dl link: https://archive.org/download/DOOM2IWADFILE/DOOM2.WAD
tested with boom202 and zdoom. works.