Joshua

Yoshiya Kiryu, aka Joshua, aka The Composer. He's one of two primordial entities whose creation was defined before the world's making. An unparalleled Mage and psychic that's created a new divine element only he can use.

Appearance
He appears in two (soon to be three probably, thanks to TWEWY NEO for giving me an older Joshua), a downscaled young-looking version, and a much more imposing transcendent angel-looking form.

Divine element
The Composer can use a special element that isn't theoretically possible, as the sheer amount of energy needed to replicate it and the necessary processor and filter aren't possible. Being unique, there is no contrary element to counter it and it can't be absorbed as there is no other being that will accept this kind of ether; it also pierces through anti-magic.

This is, in fact, the result of a condensation of an infinite amount of energy in the same area. Being hit by it is the equivalent of being blasted by the energy that created the world as we know it, thus, you would need all the existing ether in the world to stand a chance.

As such, a substance that can withstand such divinity does not exist in this world.

High-speed divine excess casting
By far his most dangerous ability. Joshua has enough accumulated ether and processing ability that does not need to perform any incantation or draw any pattern or wait for special conditions to cast god-level spells, effectively being able to spam the near highest tier of magic as one would sling normal spells; any other person would disintegrate if they were to attempt something like this.

This essentially means that The Composer can, if he wishes, simultaneously activate a myriad different unique noble phantasms and spells that do not even belong to him.

He still needs less than a minute to cast the eldest and highest order of magic utilizing the proper language. This is still much, much faster and requires less preparation than the usual casting of these spells, shortening the required time by more than 99%.

Magic Oversoul
Joshua can take over any magic in the current universe he's in or outright remove a spell.

Trivia

 * His weapon fighting style in his composer form is inspired by Terraria's Terraprisma weapon and Nier Automata's 9S's moveset.