In September 2010, the module was re-released for D&D 4th Edition by Wizards of the Coast for use in the weekly D&D Encounters sessions as "Keep on the Borderlands: A Season of Serpents". Like the original, this revised module was designed for use with the contemporaneously released "Dungeons & Dragons Fantasy Roleplaying Game" boxed set for D&D Essentials, which is oriented towards the beginning player. This time, "The Keep on the Borderlands" is set in the "D&D" base world of the Nentir Vale, in an area known as the Chaos Scar. The module is "a multi-week adventure as a set of individual encounters, each of which is meant to be run as a single session lasting 1.5 to 2 hours. [...] 'Season of Serpents' is the longest Encounters season ever, with five chapters of four encounters each, resulting in 20 total sessions of play. Considerable effort is expended to differentiate the chapters and the overall play experience; thus, PCs adventure in broadly different areas during each chapter of play. Nonetheless, many GMs found the adventure too long—mainly because it made it hard to bring in new players late in the season, something that matters more in an organized play environment".