World Building? Game industry typically talk about Lore, World, Universe, Quests, Story, Characters,etc.
Narrator could help a ton with giving lore to a player, like she could tell stories about the world/lore. Lets say you're close to enter Druid's Grove, before that Narrator might have told some stuff about Druid's Grove to a player, so hes a bit aware. Or two Character in the party might have discussed about it earlier like Astarion and Gale. "Hey, have you been in Druid's Grove, I heard the chicks are hot".
Well, world building is generally lore, world and universe stuff. Giving that information to the player and revealing more about the world they're in. To bring up another example I used earlier in the thread, at the start of Wrath of the Righteous, we have two characters casting healing magic on your character by saying a prayer, which provides world building by indirectly letting the player know that healing magic comes via faith and divinity, etc.
What exactly do you mean by a narrator? Do you mean an actual character in the game that exists to narrate and give exposition, or the standard "sourceless omicient voice talking to the player about what's going on"? Either way, I think that's a poor approach. Just having a voice telling players everything is kind of boring and impersonal. And pretty lazy. Having an actual character to do that would be hard to make believable for the most part. Though I would believe something like a magic artifact that's basically a sentient encyclopaedia, but that still feels lazy on the part of the devs. Having two characters discuss things so you can hear about them though is the kind of thing I'd vastly prefer.
