The negative energy palne is a dark place, granted. But, in the manual of the planes it says that NO light is effective on that plane, and that no one can see "clearly" more than 5ft (even those with darkvision). How are players supposed to navigate in this plane (how am I supposed to adjucate it, and ask them where to go)? I mean they cannot see good (I guess the "clearly" maybe will mean that everything more than 5ft away has concealment but besides battle...). Can the PC's see large structures (such as a giant buliding looming in the distance)? What about undead (it would be strange that undeads vision are hampered on the negative energy plane)? What about those that can see in all manner of darkness (such as devils)? The description in the DMG and the manual of the planes is vague to say the least.