There is no underdark if that is what you mean but there is a night and dark cycle in the Sphere. The star in the middle is an artificial sun which dims in intensity to that of dusk/dawn then grows bright as a noon day sun in a 24 hour period. So, technically there is a night and day even though the sun itself never sets.
Also undead are quite different in AE, especially vampires. Vampires in this setting are more like the vampires in Blade but without the sunlight weakness. They can go out during the day, but unless they have the Daylight Adaptation feat they have a -2 penalty on all rolls.