From random lore bits from the Encyclopaedia or directly ingame:

- Elementals reside within all creation, and are the organizing principle at work throughout the world. They're essentially kami (spirits).
- Twelveswood elementals are much more ancient and wise than in other parts of the world.
- They're said by the natives to be direct fragments of Nophica. Since it's folklore, maybe it comes from literally nowhere but fantasies, or maybe they do have links with Nophica herself who could have empowered or birthed them. Some people say the Twelveswood is a forest set aside just for the elementals by the Matron, in fact. This makes me think it's possible that the Shroud used to have a deeper role possibly linked to ancient Amaurotines.
- The Twelveswood is also one of the locations inhabited by moogles, who are by nature very intricate with elementals.

On sprites:
Encyclopedia Eorzea - Sprites: “The unearthly creatures known as sprites come into being given specific aetheric conditions. Whether or not they constitute a true form of life is a subject of much debate among scholars. Sprites were once thought to be kin to elementals worshiped in the Black Shroud, but it has since been proved that they are, in fact, unrelated and wholly devoid of sentience.”