From the Introduction: Basic d20 is a simplified version of the d20 system suitable for use in any d20-based campaign. This system has been designed for quick character generation and ease of play. The focus is to make it simpler for players. The GM, however, must be well-versed in the d20 system to make use of this set of rules. The system cannot be used with older forms of Dungeons & Dragons without conversion, however. This document explains how to convert your Basic d20 character for use in older D&D modules and adventures.