From publisher blurb:
Dark and Dangerous Things for Any Fantasy Game Where the Underdark May Exist Below the Surface
Designed specifically for people playing 5e campaigns.
Continuing the combination of utility, imaginative content, and deep research found in Unpleasant Discoveries and Feywild Discoveries, Evil Beagle's resident scholar and master-of-cleverness, Michael Surbrook, brings another useful toolkit to bear for Game Masters who want to elevate their games. In this case, Underdark Discoveries is an extraordinary treatise on how to incorporate the underground terrors and wonders of the Underdark into your fantasy campaign, including -
Tons of information about what Underdark beings might be enountered, how and when they might come into a game, what they might be and do, and why they act as they are wont to
A study of caves and caverns, giving GMs and players a much fuller understanding of their experiences in these beautiful and dark realms
An eleborate table for generating various Encounters and Discoveries in the Underdark and anywhere deep below the surface
That last part is the true meat of the product, as it can enhance any fantasy game with a couple of simple rolls, making it an invaluable tool for any GM hoping for some quick-and-easy help in elevating their scenario with the magic, wonder, and possible terror of the Underdark.