They are peaceful and innocent. They are creatures from the plane of positive energy, beings who replenish the life energy of those who hear their laughter.
They aren't on the elemental plane of light any longer, they were stolen by greedy wizards who feared the approach of death almost as much as the cold, eternal apathy of lichdom. When the cabal of wizards were overthrown by the kings of men, they retreated into the goblin infested ruins of the dwarven golden age. Despite their powers they succumbed the ravening hordes of goblins, and the children were trapped in the bowels of the earth.
Occasionally an adventurous sort will find one of these lost souls. Pudgy cherubic figures who waddle lost and confused in the twisting corridors of the undercity. They have radiant yellow skin and are ecstatic at the thought of being rescued. Those in the immediate vicinity of the children age in reverse and heal ten times as fast. Healing spells have double the normal effectiveness. These powers are fueled by absorbing light and heat. All light sources are expended at quadruple the normal rate (both magical and mundane), only the sun has the power to quench them without drain. The children will hover as near to a light source as possible.
Despite the decades underground, the children have been unable to escape to the surface. When there is no light, they are thought to transform into unthinking flesh rending beasts. No one has ever seen what they appear as in this form, the sound is that of a great writhing mass of worms, but others say the tracks appear as a great clawed beast. Perhaps each child is different.
The legend of the Grue is often thought to refer to the same creature by the monks of the celestial temples. It is also said that to kill a child of the light is a great crime against the entire plane, the culprit becoming immune to healing spells and any attempts to reverse life draining effects.
7 hours ago