Erebos (also spelled as Erebus) is the name for the great black walls of Hades' kingdom. Erebos is also the primordial god of Darkness and Mist.
Walls of Erebus
( http://camphalfblood.wikia.com/wiki/Erebos_(place) )
After getting through the Styx, you have to also go through the Black Gates of Erebos which is a part of the Wall of course but it happens to be guarded by Cerberus but it shouldn't be ALL that hard to distract three heads... Who knows. The Hellhound also has a tendency to eat the ghost so.... GOOD LUCK!
Walls of Erebus
( http://camphalfblood.wikia.com/wiki/Erebos_(place) )
After getting through the Styx, you have to also go through the Black Gates of Erebos which is a part of the Wall of course but it happens to be guarded by Cerberus but it shouldn't be ALL that hard to distract three heads... Who knows. The Hellhound also has a tendency to eat the ghost so.... GOOD LUCK!