My theory is his ability has to do with starlight since cleary Gisela had to use Quintessence to get Keefe to have this 'game-changing, unique' ability. It doesn't even have to do with light- oh maybe he can use all of the Points of Purities powers? But yeah it doesn't have to have anything to do with light or stars but since the creation of the ability is from the most powerful start Q it makes sense, or even if Q has another natural power that we don't know that much about. I'm definitely thinking his ability is something we've either never heard of or could never imagine bc as Gisela/Alvar says 'it is unique'
Foreshadowing his abilities-