There is a way to get infinite xp in hexxit and it is really easy. First, you need to get so armor that enchants itself by just right-clicking on it, in this case kreknorite armor.
Next, you need to hold it in your hand and right-click with it in your hand. It will enchant just like that.
Now, all you have to do is put it into the enchantment table (make sure you have a lot of book shelves) and move the sliding bar until it says a negative number.
Finally, press the letter "E" button and it will reverse the enchantment giving you xp, in the image it is -11 so I will get 11 xp. Now all you have to do it do the process over and over again the get infinite xp.
I hope this help the players and the mod pack makers. Thanks.