Blue stone that periodically glows; increases the prowess of female explorers.
If you do not perfectly succeed at a test in one of the Rituals, you might end up in the God's War. One of the possible delats is a scene of Dwarves trying to haul away a fragment of a moon rock. If you attempt to steal a piece of the stone, you might get this treasure. Be warned, it also might kill your ritualist and fail you the Ritual. As of the time of this writing (August 21st, 2018) it is not clear what ritualist abilities, if any, affect the probability of success.