The Genie Editor is a program designed to edit the empires_x1.dat file in the Age of Empires II directory. Currently, it is only capable of opening the expansion pack's data file (patched or not), as well as the data for the game Star Wars: Galactic Battlegrounds, and its expansion, which are based off the same Genie game engine.
There are two versions, but the most commonly used version is GenieEd 2, which is capable of editing things such as a unit's ID in the language.dll file, its graphics for moving, combat, and dying, sounds when selected, ordered to move, or ordered to attack, actual and displayed unit statistics, attack and armor bonuses, and more. It can also unlock the Sea Wall and the Sea Gate. The original version could edit much more, but was very slow.