It looks like Demon's Souls Remastered has at least one secret that wasn't in the original game. A new door hidden behind an illusory wall was discovered by a Redditor - the catch is that no one can figure out how to get past it.
Reddit user OrganizedBonfire posted a video clip on the Demon's Souls subreddit that shows them in world 1-3. They go through an illusory wall and find a locked door. They commented that they can't figure out how to open it and asked the community for help.
That's where things get interesting. Another user called Cosmic-Vagabond documented their various attempts to get through the door. They tried changing world tendencies, wearing different types of gear, defeating certain enemies, and various other combinations of items and actions. Other users posted their attempts as well. Yet for all of these efforts, no one can get the door to open.
Commenters have pointed out that this door is completely new to the game. It also mimics something Demon's Souls Remastered developer Bluepoint has done in the past - it added new easter eggs in the Shadow of the Colossus remake. Some believe the text that pops up - "It appears to be locked" - matches other doors in Demon's Souls that are opened with a mechanism. For them, this means that there isn't a hidden key but a sequence of events that must be completed to open this door. Others believe that this door is part of future DLC.
Cosmic-Vagabond was able to use Demon's Souls PS5's new photo mode to get behind the door and give a glimpse of what's on the other side. What they found appears to be a small terrace populated by a lone dead knight. The knight appears to have an item, but the specifics are unknown.
As of now, the door remains locked. We'll provide any updates as they come but, for now, the toughest enemy in Demon's Souls PS5 appears to be a locked door.
Source: Reddit