So the surface must be pretty dim then?
Assuming that it take a focusing crystal to re-create sufficient ray intensity equivalent to that of a sun.
That is hell of a focusing crystal! =)
Assuming the surface is as bright as present Yliakum, wouldn't amplified rays be too unbearable?
Arguably it may not be a focusing crystal too?
An extract from Players Guide/Overview of the Known World. Crystal
The Crystal that brings light to Yliakum is an enormous raw stone of purest transparency and analogous to the sapphire that hangs from the roof of the stalactite's internal cave.
A pure transparent crystal?
It's kinda ambiguous.