My Theory about the Light One
So about a week ago I asked the question on how to make the Light One and I've been thinking about it for a while and I think I have a theory.
So the Light One exists in Isaac's world where all the roles and everything else is switched including Rumple being the Dark One and instead the Light One, so we must be assuming that the creation of the Dark One must have been reversed.
So my theory on how the Dark One is made is the corruption of using pure light magic for evil purposes. People mentioned probably Merlin was the Light One, but I just believe he is a being of all out magic and fated to do so by the Holy Grail - a source of Light Magic. But not everyone can become a Dark One so it's safe to assume not everyone can be a Light One.
That means a reverse scenario has to play out. A corrupted source of Dark Magic instead being used for good purposes would make you the Light One. That also knocks out another theory of the Saviours being Light Ones, but I see that as a separate role down to Fate rather than the all out purpose.
This is also another point to add that becoming a Light One would be quite nearly impossible as using Light Magic for dark purposes but the other way around? That's hard...
Corruption of power is easy to do but letting go of dark magic is like letting go of a drug and as seen by Rumple, it's a very difficult thing to do. That's why we've never seen one before apart from in an opposite reality.