Hm… [It sounds like a candle flame going out. That imagery gives him an idea.]

[Originally, he theorized that the change in light happened because of lingering damage to the Tree. Now, another thought comes to mind.] What if the riddle was meant to give strength to the Tree? If it involved the Life Stream – and I assumed that’s what ‘heart of the Tree’ meant – and we were unable to complete it, then perhaps it’s like… a fire that doesn’t have enough wood or air to continue burning.