However, they cannot * be enhanced themselves * taken into battle * gain rapport Its also worth to note that they cannot be used to Limit Break allies or Keys. E Allies were introduced to the game with the 06/06/16 - 3rd Buster Wave patch, as a possible reward in Tower of Validation. There exist multiple types of E allies. They can be used for every grade of ally without restrictions or diffrent outcomes, but do have diffrent gold costs for each of them (same grade-differing cost as normal Enhancing.