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After doing a bit of research, I discover a completely optional area - The Upper Cathedral Ward. It is here we take on the rather interesting boss fight the Celestial Emissary, as well as Ebrietas, Daughter of the Cosmos, the latter of which proves to be the toughest fight we've encountered... so far.
At this time, Koopa Troupe has 1,313 views for Bloodborne spread across 18 videos. Roughly a days worth of Bloodborne videos were uploaded to his channel, or 3.21% of the total watchable video on Koopa Troupe's YouTube channel.