The best association for it would be the word 'Beaming' because we must include details from the sentence along with it.
There is talk about ''The caver'' and the ''treasure'' that is reflecting the light. That reflection of treasure is beaming because when it is 'beaming' it means that the object is glowing with the light. Since we are talking about the cavern, beaming light reflected from the treasure is eliminating the darkness from the cavern.
