the easist way is get an lv s hymn crystal
and that crystal is dropped by the child of light
so go to plasma bell
and go to the place where you defeat child of light
(on phase 3?)
she will ask you to battle if you accept it and defeat it it takes time to have the challenge again
so in the meantime it's better if you search the akhasic record on the plasma bell
(the room before you face child of light)
Note: i have 30 akhasic record and 40 lv s hymn crystal^_^