From A History of the Known Lands, Volume One, Book One
Introduction by Librarian Lapo of Eseti, Principality of Thellerg
As we stand now in the year 173 since the unification of the human kingdoms by the hand of King Aros III of House Videson the scribes and sages of the Library of Legend feel it necessary to begin the process of documenting the history of the Known Lands. Since any previous histories were typically local in nature or are highly outdated by modern standards (with many predating the fall of the Old Elven Empire some two millennia ago) the book you hold in your hands is the initial volume to a document which may never see a truly "finished" state. An in depth history of the Known Lands of Ilyenor, so that all may know the history of our world and may learn to stand upon the shoulders of those who came before us.
The World of Ilyenor (or, more specifically the area of Ilyenor known as the "Known Lands") is a setting for fantasy role-playing games. What I found in my time playing was that while there were many games with excellent mechanical toolsets they tended to either ignore broader areas of background and setting, or become overly specific with their particular vision of what the setting should be. This tended to lead to situations where trying to introduce stories created by a particular game master for a particular group of players would either spiral "out of canon" by failure to conform, or exist in something of a vacuum where if you wandered too far to the edges of the sandbox the amount of detail about the world would suddenly drop off leaving game masters in a position of needing to improvise a large amount of setting on an ad-hoc basis (again, leading to issues with consistency and tone over time).
After taking an extended time off from RPGs and coming back to them I wanted to run a campaign but was aware of that potential problem. As I was reading through the Game Master's section for Dungeon World (a phenomenal resource for people running a fantasy RPG, regardless of system, in my opinion) I was struck by one of their "Principles" for running the game.
Draw maps, leave blanks.
In essence, pre-plan enough about your game world to know where things are and maybe some highlights of a particular place, but avoid detailing out everything about the world. Know in broad strokes where the capital is and who rules, but don't bury yourself in the details of every aspect of governments and the location of every village and farming town. Knowing where a big river is, but leave yourself the ability to add smaller ones as needed, so to speak.
That's what Ilyenor strives to achieve. More background and setting than may be provided by many fantasy RPGs, but done in a way that paints broad strokes and leaves you space to add the fine details you want for your particular campaign.
With that said, I set out with some design guidelines of my own...
Almost every fantasy RPG system on the market includes elves, dwarves, humans, wizards, dragons, rules for magic, and epic battles. When you're playing in the world of Ilyenor you shouldn't ever need to re-learn alternate versions of any of that.
In the past there have been a number of products that I've loved. Unfortunately, even when they were built for rules systems my friends were familiar with I found that because of the learning curve to the setting itself, it was never going to work out to convince them to play in them. (Settings like Dark Sun and Spelljammer for the second edition of AD&D spring to mind, for example.)
The general idea behind almost every RPG in existence is to get together with a group of people and tell a story, together. One person may provide the overall direction, but everyone at the table has some sort of input. Playing in the world of Ilyenor should enable you to do that with as many options for telling your stories as possible, without introducing new complications or mechanics specific to a game set on Ilyenor.
Finding the right collection of game mechanics can be highly-dependent on a particular gaming group. I wanted to make it possible to use Ilyenor with as many options for underlying mechanics as possible. The main portion of the setting doesn't contain any system-specific mechanics at all and the various appendices should provide the mechanics needed on a game-by-game basis.