I think, since rainbows are simply the refraction of light and separation into different color spectrums through water droplets, they would appear in Yliakum as well. Because there is light and rain, but if they \'d look the same as here on earth depends on the type of light that is emitted from the crystal. The colors could be in a different order or completely different at all perhaps.
As for nighttime, I haven\'t found it to turn completely dark at all. Actually I don\'t even think it turns dark enough at night. Of course me being a creature with nightvision that might explain it but I thought nightvision wasn\'t implemented yet.
Either way complete darkness is a bit unplayable unless we create portable lanterns, etc. which might be a nice idea.
So option one: At night it turns completely dark, except for those with night vision. For the others you either have to stay near any light sources like campfires or crystal lanterns or you have your own portable light source, with limited range of course. This would make it so that at night everyone with a lantern or torch has a limited range of view, in a sphere around the person where they can see. While others out in the dark only see the carried light source as a point. This could make for some nice ambush planning and stealthy attacks.
Option two: It never turns completely dark but the crystal either lets through light from the surface moon or has some sort of minor fluorescent properties allowing it to store some sunlight during the day and emit a dim light at night. That way all creatures have a limited vision even at night, away from any light sources.
