Hello all, It is possible to create new leader traits by simply modifying the XML files. You can't do anything you want, but I found some interesting ideas that really add something new to the game. Here is what I tried : 1. Free upgrades : all your gunpowder and melee units get the free "Great General" Promotion. This means you can upgrade them for free (I made a Rifling beeline which was quite efficient). You also get access to the great general promotions, such as Tactics (+30% withdrawal chance, which is nice, but not game breaking), and Leadership (+100% experience gained from combat, which is not as powerful as one may think). This one is not very powerful, although quite fun. I combined it with idea #2, and then it became too powerful... 2. Productive trade routes All your trade routes yield production in addition to the normal commerce. Although the numbers could be changed, I found this trait to be balanced with an amount of additional production equal to 50% of the trade route value, rounded down. For example, if you have a trade route of value 3 , you get an additionnal 1. 3 with 6, and nothing with 1 trade routes... The strategy with this trait is to beeline writing : open borders are very important, since domestic trade routes usually yield 1 in the beginning. Other nice goals : The Great Lighthouse, Currency, Compass (for Harbors), Optics and Astronomy (to find distant neighbours and get additional benefits from trade routes, Economics (for Free Market, and Custom Houses). 3. Extra food : +1 to tiles that normally yield more than 4. This one may be too powerful, especially if you start near floodplains. Just irrigate them, and turn your cities into specialist or production powerhouses. The must for SE players. And after Biology, even irrigated grasslands yield 5 (which make these tiles better than a grassland town, at least under representation). You won't experience the post-Liberalism lag you usually get with an SE ! I don't have the code in front of me, so I can't put it here. If you're interested, have a look at the civtraits.xml you'll find in your Civ4/Warlords/Assets/XML directory. I think you'll guess how I did that alone. For idea #2, however, try to find something called <TradeRouteYield>. It seems like Firaxis developed it, but never used it. You can add extra food, or extra commerce as well, but I prefer the idea of extra Enjoy !