The Imperial system, known as TIS for short, is a d12 based die rolling gameplay and drama system for RPGs. It aims to facilitate games with collaborative, co-created lore and history, built from a limited description of the world. As such, players should feel free to describe friends they know who can help with challenges faced, to fill out the details of a treaty between two peoples which can aid them in a situation, or describe how their personal history influences the story.
This system was created to run Triumvene, a cross-genre RPG campaign we've created as a partner for the system, set in an industrial revolution science-fantasy world, intersecting with places of high magic and high technology. However, it was also set up to be generic enough to allow for any world to be created with it. If you want to use The Imperial System to run a campaign set in the world of Star Wars or Lord of the Rings; Game of Thrones; Critical Role's Tal'Dorei campaign; the WotC D&D adventures, or something entirely new from your own imagination, then you can do that too. It's a system geared around creating a style of play, rather than providing play for a specific setting.
Here's a pair of reference for players, covering the most common things you'd likely want to know. The detailed rules are everything after.