From publisher blurb:
Cawood Publishing presents Monsters of the Underworld for 5th Edition! 110 new monsters and lore about the dark realm. From the Lava Dragon to the Lich King, from the Flying Ogre to the Giant Queen....this is a unique collection. Featuring the incredible art of Travis Hanson.
Brave the Darkness!
This 129-page full-color book includes:
General lore about the Underworld
Game Master's Advice
Adventure Hooks
110 new 5E monsters with individual illustrations, stat blocks, and bios
Undead, Dwarves, Orcs, Drow, Duergar, Deep Gnomes, Dragons, Giants, Fiends, Elementals, Constructs, etc.
CRs 1/8 to 30
Ranger and Druid subclasses
Encounter Tables
Underworld Maps
Lore about the Underworld Races
Flora
Locations Table
Events Table