Boss/portal location exploit. In Hellgate, it takes sometime to fight through all monsters and locate the portal that will lead you through each level or perhaps locating a boss that randomly spawned. You can save your time and effort for that hassle and do this instead.
Currently, in Hellgate, you are allowed to resurrect as a ghost after you died. And unlike WoW, you can see normally even though you are a ghost. What could this advantage brings? It means that you can cheat the randomly generated map system and locate anything inside the map including portals to boss or next level while you are a ghost.
So if you want to save your and your group mate time running through each levels, you can have someone die and spawn as a ghost to check the path in advance then resurrect and fight a direct path toward the boss or portal without wasting your time locating them.