The standard name for the Symphonic Information Viruses. They are created in the tower, and can travel through symphonic lines, a network that runs throughout the tower. The more advanced viruses are even able of using Flip-Flop Conversion technology to appear in the real world and physically attack humans. Lyner and the Knights of Elemia are called out when these viruses appear on the real world.
Most of the time, viruses come out of a place called the Altar of Apostles. Since viruses are programmed to harm humans, whether they manifest in the real world or not, they are usually a threat to the people. If they do not take a physical form, they can invade the guardians of the tower and take control of them to attack people.
These are Viruses that have taken a Human form. They also have emotions and are capable of rational thinking, even going as far as rebelling against their original programming. So far only two have ever appeared: Ayatane and Kauron.
Elma-DSThe name of the virus that appeared at the beginning of Ar tonelico: Melody of Elemia. The most important characteristic about the ELMA-DS is that it can freely use Flip-Flop Conversion.
Flip-Flop conversion is a technology which can transfer objects between the Binary Field and the real world. In other words, it can change objects into data, and data into objects. Therefore, ELMA-DS will escape into the Binary Field to avoid physical attacks, and come back in a tangible form when it decides to attack. The Hymn Crystal Purger can stop it from taking this kind of action. Lyner descended onto the Wing of Horus in order to go find this crystal. Mir treats it similar to a pet, and it's also a dark version of Shurelia's strongest tower guardian ELMA. However, ELMA-DS has shown to be stronger than ELMA, being able to brainwash it, and even summon clones of ELMA to support him in battle.