Lance McDonald, known for digging through early versions of Souls games to find unused content, has pieced together some unused enemies and earlier versions of bosses in DSIII.
A lot of what is shown appears in those early leaked screenshots before the game was officially announced. Oceiros and Baby Ocelotte are fully modeled and functioning, Vordt of the Boreal Valley initially had a slight alteration in his design, both bosses featured unused music. He also shows off some never-before-seen enemies, a hostile pilgrim, and a hollow-filled slug that is strangely reminiscent of the cramped coffins in Yahar'gul.
The last big discovery he made a video about was the cut boss "Snake Ball" from Bloodborne.