Abridged History of the 10th Age
One of the ancient Elder Races, the three that existed before the creation of the demi-humans or the arrival of Man, the Trolls have lived on the face of the world since before there was light. They worship Mother Night, a primordial force of darkness that has since been reduced in her might – the arrival of the stars signaled the long downslide of Mother Nights power; she is now banished during the day due to the Lamp of the Sun and weakened at night due to the Disc of the Moon.
Trolls find holes and caverns pleasant to live in, as they protect them from the cursed light of day. Indeed, many trolls dwell in the Underdark, but they are a fiercer and more horrid breed than those that live upon the surface.