From the back of the book:
The deceptive safety of the surface cracks. Fearsome creatures rise from the depths, spurred by opportunism or malevolence. The Netherworld can no longer be relegated to faraway abysses and legends...
Incidents in mines, disquieting sounds in basements, curious disappearances, dried-up sources... Mysterious phenomena of this nature will have the adventurers undertake dizzying forays into ghastly tunnels and gloomy caverns, where danger does not always lie where one might expect it to.
Resurgences of the Netherworld is a collection of five adventures intended for characters of levels 1-5, powered by the rules of the 5th edition of the most mythical role-playing game.
Standalone. The adventures featured within can be played as one-shots or easily slotted in a long-running game, whether for a short autonomous session or as part of a campaign exploring the depths of the Netherworld.
Ready to play. The adventures of Resurgences of the Netherworld require the Adventurers and Grimoire books (or any other core book containing the 5th ed. rules) to be played. No other resources are necessary: all featured perils, creatures, optional rules, and magic items are described in appendices.