Invisible Sun is one hell of a game. Unfortunately (?) the developer has been deliberately light on to maintain mystique. The game itself is a premium one-click entry for a whole gaming group, including x4 Hardcover Books (The Key, The Path, The Way, The Gate) which represent the Player Handbook, GM Guide, Magic Guide and a Game Mechanic / Worked Example guide, GM play book, 1000 cards, Char sheets, restaurant menus, business cards, wax sealed envelopes, 6 finger statue, tarot deck of suns plus many more high quality props ( why not pick up a tourist pamphlet of the city?).
Uses D10 rather than D20 (with 10's replaced by 0's, so rolling from 0-9) and uses a different take on rolling for scores: the challenge (e.g. level 5) subtract the venture (e.g. spell level 2) means a roll of 3 is required. This then extends across including multiple dice and eating into stat pools called bene. There are qualia (mental) and certes (physical) stat pools, with experience measured in terms of joy, despair and crux rather than experience points.
Every character is a spellcaster, with access to normal spells plus one of four major schools: vance, weaver, goetic and maker with apostates a hybrid of all. Characters have traits: eg "hosts a legion" you are inhabited by 1000 demons and have a subset of magic skills with a new skill tree on top of your order specific magic. The first session is usually spent creating the characters and their histories. Go. Explore the 9 suns and their planes.