From the publishers blurb:
An adventure for 4 to 6 characters of 1st to 3rd level, Chamber of the Serpent can be played solo or with a group, with or without a GM.
Delve into the dark depths, explore ancient halls and chambers in search of gold, glory and adventure! But beware the hazards and horrors that guard the Chamber of the Serpent! Chamber of the Serpent is an adventure site and includes a map, details of the major encounters, more than a dozen tables, new monsters, treasures and more! In addition, the set also includes 9 cards which provide the details for all the new monsters, spells and magic items. If you want to play with miniatures, checkout Across the Realms Floorplans and Geomorphs, which gives you everything you need to lay the dungeon out in miniature.
Chamber of the Serpent is the first in the Deadly Encounters series, which is part of the Old School Adventure line.