Metyr was corrupted by the frenzied flame

[Thomas Devlin]

It's never been a secret that the two fingers are defective in some way, people have been telling us that since the base game, but after the reveal of Metyr in shadow of the erdtree I think I have a theory on what exactly happened to them.
Ymir's quest gave me some serious questions once I started thinking about things, the first thing I noticed when looking at the map is that there are three finger ruins, two if them are above ground visible on the map, and there's a third one buried beneath Manus Metyr, three finger ruins. Ymir also specifically reffers to Metyr and the two fingers as "unhinged" and "unsound", those could just be adjectives, but madness in the lands between is associated with the frenzied flame, so unhinged seems like an awfully specific way to label them. My final piece of evidence is simply the fact that all finger creatures are children of Metyr, and the three fingers definitely falls into that category, so you can imagine that the three fingers probably came from Metyr.
Allot of people theorize that the nox tried to kill Metyr and that's why she's broken, but I believe the event that broke Metyr was her becoming corrupted by the Lord of Frenzied Flame, and the inciting incident that led to her being abandoned by the Greater Will was her giving birth to the three fingers and introducing the frenzied flame into the world

[Old Captain Yon]

"The mother of all Two Fingers and Fingercreepers was in turn a magnificently gleaming daughter of the Greater Will"

I think that Metyr has no connection whatsoever to the Three fingers, since she is only mother of the TWO. Three fingers seem to be something else entirely, something opposite to the Greater will, and since their influence is always very obvious, I honestly doubt it. DLC has the frenzyflame area, and it is drastically different.