Terrifying ghosts were ghosts summoned in Death's mansion by Melzar the Mad during the 2014 Halloween event.
They had 5,520 life points and defeating them awarded 50 reward points. They inflicted a passive 1 fear to players near them. They also had a special attack where they summoned a green fog on the floor, whereupon any players standing within a 3x3 area of the spot they attacked would be dealt 5 fear and sent scattering away in various locations, similarly to a wailing ghost.
This information has been compiled as part of the update history project. Some updates may not be included - see here for how to help out!