Lago or Ultranate is a powerful artifact that Aika Sumeragi found before the series started, but after AIKa Zero. When it's in danger, it (or she) will transform into Shivie Aika to protect her. Rudolf tries to reproduce it with Shivie Neena.
It's a liquid metal armor that bonds with it's host and giving the enhanced abilites.
Anyone that uses it for too long will get their body destroyed not matter how powerful you are. Aika may be an exception due to her uniqueness.