The Vendrizi are symbiont life form that joins with a willing host. They were created half a million years ago by an unidentified race to be living records of history. They have travelled the galaxy from one host to the next since then. They resemble a meter long insect shaped like a short spine with a pincer-like head. The spike-like things on its side integrate directly into the chosen hosts neural system. Being composed of 100% genetically neutral material, they can coexist with any organic life form. They can cure their host of most physical problems, diseases and enhances their faculties. Once linked, a Vindrizi can be separated from its host, but cannot take on another without doing extensive neural damage to it.
Source: Babylon 5 Universe