You gain intelligece XP every time you mine, kill bosses, kill players, win last man standing games, or whenever doing minigames, everything you do will gain you intelligence XP and through that you can forexample do certain quests/missions, you can attack certain bosses, get access into certain areas and also get advantages of fusing stuff, meaning that if you are for example lvl 40 intelligence people can pay you to do stuff or buy stuff for them in certain places they dont have access to for a good profit, so depenting on how active you are in the game you will therefore recieve some good intelligence XP. Furethermore we are still improving it and making it wider, meaning that we will be adding som smelting stuff and more in the skill dimention approach, stay tuned for the last update before the release!
Much appreciated man!