Orrery is a system using Troika! backgrounds to generate characters, and which can be (and hopefully will be) used to play in the implied setting of Troika, but which otherwise is a completely different system. Orerry is also a “build” of Schema, customized to this purpose. To play Orrery, you roll a background in Troika, put it on an Orrery sheet, note a few things, and off you go. The Guide (Orrery's GM/DM/Etc) will use the setting material from Troika in whole or part, and away you go. Troika is published by the Melsonian Arts Council; Orrery is an independent production of Levi Kornelsen and is not affiliated with the Melsonian Arts Council Source: The Developer Website.