These symbols exist in two forms: one, they are the symbol of the realm that they exist in, and two, they are the sigils that appear on the souls of the Elementals chosen by Fate.
Yes - when an individual has been chosen to be an Elemental, their soul will bear this marking. However, not just anyone can see the marking. When an individual is chosen, they will be able to see it in their own reflection (side note: it doesn’t have to always be visible to them when they look at themselves lol). But how will people know that they are telling the truth? Typically speaking, the current sitting Elemental will be able to sense and see their successor. There cannot be more than two individuals with the Elemental Sigil on them, but there cannot be more than one current sitting Elemental. A successor can take on the role of Elemental under certain circumstances:
The Current Sitting Elemental (Predecessor) dies, thus the role is given to the Successor.
The Current Sitting Elemental (Predecessor) renounces their role and title of Elemental, allowing the Successor to take on the role.
When a Successor is identified, it is not always a death sentence for the Predecessor (although, some Realms do believe that). The Successors aren’t always announced to the world, out of their own protection. Additionally, Predecessors do not always have a say in who their Successor is, as it is something predetermined by Fate itself. (And, as Haseo would put it, Fate is something that cannot be tampered with. Things always have a way of occurring, not matter how hard you try to change it. Otherwise, if one thing is changed, something else must happen.)
Can a Successor denounce their role?
When someone is identified as an Elemental, they are given an opportunity to accept or denounce their role. It doesn’t remove the marking from them, it just means that Fate will end up continuing the cycle. There are a few characters in the story who denounce their role and try to live a normal life as best they can.
The problem is that Elementals are believed to be the pinnacle of their elemental power. While this isn’t always the case, Elementals are, by design, some of the most powerful creatures, just short of the gods themselves.
There isn’t really a special phrase or ceremony to “awaken” the sigil, although by tradition, the Realms each host an “Awakening,” a ceremony to honor and recognize a new Elemental. When a Successor accepts their role, their sigil becomes more prominent to those around them, allowing more people to actually see the sigil on their soul when their power surges. If the Predecessor is still living, the sigil becomes dimmer on their souls once the Successor rises.
Basically, it’s a whole “spiritual” thing about accepting one’s self and the role they play.
Now, that all being said… there are certain individuals who purposefully don’t announce that they are the Elemental, most specifically the Mind Elementals. When this character is revealed, they are the first to point out that Mind Magists are paranoid individuals by default - to have someone more powerful than them is a terrifying concept because that means that they can not only overpower their own powers, but they can read EVERYTHING. Thoughts, intentions… and yes, sometimes the future. Individuals with that much power are perceived as a threat.
But the Mind Realm is just one of those circumstances. And the idea that their people would come after them is also paranoia to the highest degree. (The Current Sitting Mind Elemental chooses to hide their identity for a multitude of reasons, namely because they witnessed the death of the previous Mind Elemental, and because they fully recognize that if they are captured, their own power could be used against them by those who seek chaos).
Who can see the Elemental Sigils?
Aside from the Successors and the Predecessors being able to see each other’s sigils, there are a few other individuals that can:
The Greater Gods (Xavier - God of the Heavens, Isynea - God of the Middle Realms, and Rikiru - God of the Afterlife)
The Lesser Gods (Attar, Leviathan, Asmodeus, Belial, Mikhael, and Mephistopheles)
The God of Time and Fate (unknown)
Din (who can see the Threads of Fate)
Some of the more powerful angels
The demigods who are the direct descendants of a Lesser God (first generation offspring).
Anyway. I had fun trying to design these, considering that patterns are not my strong suit!