An omniscient narrator is an authorial voice outside the characters and the story that can move between the characters and places at will. This is slightly different from limited omniscient narrator which is outside the characters but we’re also limited to the perspective of one character at a time with a distinct break between each characters’ perspective. A famous example of omniscient narration is Dickens whose authorial voice jumped across space, time, and characters, of which he had hundreds.
Another name for omniscient narration is the ‘reliable’ narrator. This is a problematic definition though because the principle of the ‘reliable’ narrator works on the presumption that the authorial voice is objective and truthful. Firstly, the omniscient narrator is not always objective/unbiased, Dickens is known for pointing out the suffering of the poor in his works, therefore his narrative voice couldn’t be considered unbiased, though it is truthful. However, being truthful also suggests that the narrator hides nothing from the reader; if this were so there could be no twists in the tale because readers could know everything from every characters’ perspective. So the narrator isn’t entirely reliable because there is always something they’re not telling us. If a narrator is deliberately withholding information how can they be reliable?
Part of the idea of the ‘reliable’ narrator is in comparison to first-person/subjective narration where we are confined to the perspective of one character. Theoretically this character is biased, has their own motivations and just generally wants to make themselves look good. This can all be true but, as with Dickens showing the plight of the poor, omniscient narrators can have their own motives too and be biased. Another example could be the hero looking heroic and the villain villainous. We may get to see part of the story from the villain’s side but this still doesn’t mean they’re going to be painted with the same balance as the hero. Quite often we will see them enacting a part of their evil plan, such as the scene where they send someone to get rid of the hero. We’re likely to see more scenes of the hero doing ‘good’ things and the villain doing ‘bad’ things, which may not be entirely accurate because the villain isn’t always evil they’re simply the hero’s antagonist. If the narrator is deliberately trying to make us root for one character over another can they be objective and reliable?
Omniscient narration isn’t as simple the narrator being reliable and honest or unreliable and dishonest. As with any other form of narration there are various different techniques that can be used to create different effects. We can make our narrator as reliable or unreliable as we want, we can even use reader expectation to our advantage as readers will expect an omniscient narrator to be completely truthful.