On second thought, this umbrella tag seems wrong considering that they're described as sisters and the wiki says they're treated as separate characters.
On second thought, this umbrella tag seems wrong considering that they're described as sisters and the wiki says they're treated as separate characters.
They are sisters and two separate characters in the manga and anime but originally Materia was meant to be a base model with 2 versions and then later another dark-skin version based on the white version. Just think of the umbrella tag Materia as the base design where all other Materias are made from, you can technically have as many Materia as you want like post #2701652. The manga/anime just makes two specific Materia characters out of many possible Materias, each having one of Materia official design version.
Another way to look at it is if Fate released Saber and then Saber Alter first as action figures meant to be different versions of a single Saber's base design and then made visual novel/anime later with 2 separate characters based on the 2 design variants.
Or you can think of it as Materia being a "type" or "species".
There are arts where both Materia sisters are depicted with another different Materia like this or where they only way to distinguish the Materia is minor details like the "gloves" like here. It can be imagined that a monochrome lineart drawing of the Materia in the base design with no hairclip would make it impossible to tell which Materia it is and only the umbrella tag can be used.
Thankfully, there are more differences between the two than just color in this case or else fanart like this, which just makes up their own color scheme, would be quite problematic to tag.
I'm actually not sure if we want to go 3 layers here or to put this tag at the same level as the other two tags. Since it is still technically just a dark-skinned version of the White version, I'll make this BUR for now.