In Vol 4 of Log Horizon (near the end of Season 1 of the anime) Shiroe invents a new class of world-level magic by using his skill as a scribe to create a magic contract. It allows non-player character Rundelhaus Kode to become an "Adventurer", establishing a possible precedent for converting pieces of the game into elements of the real world. Regan, the Sage of Miral Lake, notices this from a distance and later remarks to Shiroe that to his knowledge this is only the fourth example of world-level magic ever used. But Regan also says that at about the same time he noticed another similar event somewhere to the west. This was taken to mean that someone, probably in the city of Minami, had also invented a new piece of world-class magic, presumably the fifth ever example. Given the tension between the two countries it seemed this was going to be a major plot point, but I never figured out exactly what who it was or what they invented.
Shortly after that it becomes clear that Nureha (a.k.a Darielle) has a magical ability to disguise her identity that is outside anything Shiroe knows about. She is a magic-user from Minami, and this is apparently new magic. But clever disguise seems way less than a "world-level" discovery. It seems more more like an example of the next-level abilities that are developed by other veteran characters in the following volumes, like Akatsuki's shadow strikes or Souji's ability to foresee his opponent's next attack.
Am I missing some hugely important implication of Nureha's disguise? Have I overlooked some other new magic discovery by the Minami faction?