Darth Ghost was a Sith Lord who died when something PWN3D it in the head. It became a Force ghost but it lost its memory. So it didn't know its name anymore. Darth Ghost is nothing but a cape because only its eyes are visible. But not really, because you can see the outline of its ugly mug too.
It's widely believed that the greatest mystery of the galaxy is Darth Ghost's gender. Hundreds of researchers have
wasted their time invested millions of credits and spent their entire careers trying to discover its gender. It is believed this information will aid cancer research. Unfortunately, because this science is so incredibly complicated, many people have, like it, lost their memory this way. It didn't help that came and it hunted anyone who tried. Would you want that thing whining in your face well you tried to work!? Would you!!? Didn't think so. Wookiee Goldberg once tried his/her own method of discovering its gender, and was as a result severely PWN3D. Some scientists also believed it's real name might be a clue to finding the Valley of the Jedi, but this is pure speculation.
After Darth Anonymous died Force laughing by himself, Darth Zada was haunted by Darth Ghost. Darth Ghost wanted training of Darth Zada. When Darth Zada died, Darth Ghost was trying to find a new master.