"There are a few reasons, the most basic one is how hard it is to increase the affinity in any of the elements, but apart from that, those two elements, light and darkness, if we can even call them 'elements', are harder because someone only can increase its affinity with them after they already had affinity with all the other elements, that, unless, if you are born with a high affinity with one of them, which is as rare as someone been born with all the basic elements in high affinity" said the professor, taking another sip from his Koppi.
"So.... in sum, or you are born with high affinity in light or you have to increase all the basic affinities before attempting to increase the light affinity...."
"Correct, as you can guess, both are extremely hard to come by, after all, the main ingredient to the elixirs are..." the professor was about to talk about warlocks when he realized he was talking too much already. "...hard to find."