Back during the PlayStation Experience in 2014, director Hidetaka Miyazaki himself showed off footage of Bloodborne's Chalice Dungeons. This was months before the game finally came out, and in the demo, it showed a big enemy with a burning blade hand and a bad attitude. However, it was thought he was cut from the game as after years of looking by the community, he was nowhere to be found… until now.
The enemy was spotted by player KolbrotKommander in a dungeon and YouTuber Moros Nyx showed off the discovery. Under the video, it is explained:
On 19th November 2017, a group of Tomb Prospectors, led by KolbrotKommander (the creator of the dungeon) made the impossible discovery by officially sighting the first ever Flaming Undead Giant in a Depth 4 Cursed and Defiled Root Chalice.
This video explains the situation pretty well, and you should definitely check it out.
It's extremely rare, obviously, but you can check it out yourself by using glyph pa6ssc6u. The discovery has opened a conversation about if the putrid depths of Bloodborne is hiding any more undiscovered nasties. That is a pretty exciting prospect.