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 other gaming systems without conversion, however. This document explains how to convert your Basic d20 character for use in Chaosium's Basic RolePlaying Game modules and adventures.