Villains who are omniscient are capable of unlimited knowledge; they literally know anything and everything. Any villain in this category can and must be labeled as "All-Knowing" in the story that they are in.

It is not uncommon for Omniscient villains to be beings of great or even god-like power, or in some other cases, Lovecraftian horrors whose very nature and power are completely unfathomable. Also, because of their incredible intelligence, they can very often be amazing strategists or even master manipulators and/or Masterminds. This can make these villains both hard to deal with, as well as extremely dangerous and capable.

Omniscient beings have imaginary and conceptual limits, however; most specifically, they cannot (unless certain ones have the abilities to do so) predict the future or read minds, meaning that their powers are restricted to what exists in their own thoughts and current space/time continuum. They can also be self-aware of their fictional existence.