Elements and Visions

Although officially, there are 7 elements in Teyvat, that is not to say there aren't other elements, albeit unrecognized or outside the dominion of Celestia. Recent sources from Enkanomiya have hinted on primordial elements of "Light" and "Darkness".

We have also noticed Dainsleif, Lector and our sibling exhibit the ability to transcend through portals, hinting at a potential element of "Space". They also exhibit an unknown "dark" power which could potentially indicate presence of an unknown element.

There's a Nameless island near Mondstadt, as well as Thousands winds temple, where people used to worship God of Wind and Time. Hinting, there could be a potential element of "Time".

Every being with the ability to control elements makes use of one of these elements, with the Traveler being an exception, who has the capability to control Anemo, Geo, Electro and Dendro (so far). In battles, one must be mindful about combining elements accordingly, to create powerful elemental reactions which can be used to overpower one’s foes. Hence, it’s important to consider how these elements will synergize.

From the point of view of science of Teyvat, the elemental affinities of multiple wielders of the same element passively combine into Elemental Resonance, enhancing the synergies and applications of these elements.

Some beings, mortals or otherwise, are granted what’s known as a “Vision”, which in the world of Teyvat, is seen as a gift bestowed to those who’ve been recognized by the gods. Visions grant the user the ability to manipulate and manifest the element of their given Vision. It is said that Vision holders, (also known as allogenes) have a chance at attaining godhood and ascending to Celestia (reference: dialogue with Venti). 

The exact criteria on how one is chosen/granted a Vision is not yet known in-game. However, it has been hinted by the archons we've met so far, that Visions are given as a form of acknowledgement by Celestia, and that, the Archons do not have direct control over granting these out. "the key is people's desire" that resonate with their respective vision, and another aspect yet to be known. 

It’s depicted that upon losing one’s vision, regardless of whether they willingly or unwillingly forfeited it, seems to have severe consequences, such as losing critical memories from the time they wielded the vision, and/or losing their ambition.

While it's rare for vision holders to possess more than one element, it's not impossible. Apart from Traveller, Kazuha has also exhibited possessing two visions of different elements simultaneously, albeit for a short period of time.