The Shadow

[Sessika]

I took a look through the Super Secret file and there is only one PDF file. The 'ancient game overview' which is old concept material from when the game was referred to as "unknown", much of which did not make it into the final finished game. In the file I couldn't actually find anything about the shadow or a guardian and even if there was, given the nature of the content of the file it couldn't be taken as canon without confirmation from the devs.
I may have missed something but so far as I can see there is nothing in the super secret file about the shadow.