OK so here is the current concept for Dark Souls hardcore mode,
1: You start the game with a small amount of items that are now needed to resurect at a bonfire or to restore your HP estus and spells at one, each boss drops a few more of these items dying with none of them in your inventory results in the game resetting story progress back to when you first arrived at fire link shrine, all key items are put back in their places but other guaranteed items environmental loot shop inventories ect doesn’t respawn you keep all your levels and loot,
2: Several key areas receive a table of enemy deployments they can draw on, including enemies from neighboring areas, making it harder to predict what is to come, this pool expands with each slain boss,
3: New miniboss level enemies are added to areas and patrol over a large area, these enemies spawn in more frequently and with higher stats the more Bosses you kill,
4: all Bosses are permenately in their new extreme forms(A new mechanic for the remaster where every boss has a new super powered variant you can fight after killing them once normally) things like Ornstein and Smaugh both having 50% more HP and when the extra HP is depleted they go super form meaning you can end up facing both super forms at once ect,
5: Killing Manus and Priscilla become prerequisites for facing Gwyn,