Elden Ring, like every other From Software game, will feature a protagonist who is going to have a special title.
From Software is known for creating a universe within which the protagonist is never the hero. Rather it is someone who has the choice to drive the world in a certain way to facilitate efficiency.
For instance, the chosen undead in Dark Souls can either plunge the world into light or into eternal darkness.
The world will not drastically change, but it will continue a cycle which has been going on for ages.
The Tarnished in Elden Ring is very similar to other Souls series protagonists
In Dark Souls 3, the unkindled one is a person who has failed to link the fire. However, he or she will have to fight through the enemies and do what is needed for the world to proceed.
From Software’s emphasis over natural cycles is what makes their protagonists unique. Sekiro however differs from this formula as it is not an RPG game, rather an action-adventure game which has certain Souls-like features.
Bloodborne has a hunter who is not unique but has the drive to do something which several others have failed. However, ultimately even the hunter is trying to work towards a natural cycle that will ultimately help the world to function.
In From Software games, the world defines the character and whatever the character does is to ensure the sustainability of that world.
Within Elden Ring, a similar ideology is probably going to be implemented as well. The Tarnished is also going to be someone who will help restore balance in the world by ensuring that the natural cycles are intact.
The key feature of the game is obviously going to be the Elden Ring which has been shattered and it has led to some unwanted instances within the world. It is clear that the trailer speaks about an unending curse where life and death is going to keep continuing within the world of Elden Ring.
The Elden Ring was the one which provided life to this world and its shattering has probably led to the curses that are spoken about in the trailer. It is possible that the role of the Tarnished will be to restore the Elden Ring itself.
As it says in the end of the trailer, the protagonist is supposed to “brandish” the Elden Ring for everyone.