Inside the Mind of Mattlantis

This one's pretty fuzzy, I only got 5 hours of sleep. First, I was watching a girl, somehow become more and more corrupt and evil, in some sort of garden with a fountain, maybe in the courtyard of a castle. Then all I remember is something weird happened that made me want revenge, so I got a sword, got pumped, and jumped into some sort of original Legend of Zelda fight between myself and this thing.