Uh...as far as I know (I have completed the quest and go into the passage myself), you don't need to interact with the NPC somewhere in A1 or something in Legandary Corinth. The guy in A1 will only give you the HINTS on how to find the items. But if you are careful (and smart) enough, you can find them without hints. Well...one of these is a bit difficult if you don't have any hints, but yeah I think finally you can figure it out.
And you can complete this quest (actually not a quest, no quest log or quest reward) in NORMAL.
For those who found the hints but cannot understand them, here's my hints. Hopefully this will help you to better understand. SPOILER ALERT!
One parchment records the places to found piece 1&2, and the methods to open the locked doors of piece 3&4. The places to find piece 3&4 are recorded seperately on the other two parchments.
ULTRA SPOILER ALERT, DON'T CLICK IT.
Ptolemy&lighthouse -> Alexandria -> Rhakotis.
Poor people -> slum.
Broken walls -> you can break a wall.
So the piece 1 is located at somewhere in Rhakotis Slum, and you can break a wall to find it.
Tao -> Jade Palace in Qiyun Mountain is a famous Taoism temple.
Go to Jade Palace waypoint, the correct way to find Jade Palace is to go lower left, so the opposite way is upper right. Go upper right and you will find the second piece in a cave.
Seashell&Aphrodite -> birth of Aphrodite -> Sea of Marmara (honestly I don't know how these 2 are related but it seems this is the closest explaination) -> Propontis(ancient name of sea of Marmara)
Piece 3 is located in a cave called "Great Hall of Propontis" near Medea Forest.
There is a fountain near the locked door, so apparently it is the key to open it.
Eye sees a path -> eye of the Grey Sisters is used to see the path of the player in main story.
So kill Grey sisters again, pick up the eye, and click the fountain. The door is unlocked.
"Hade's door" is kinda vague. At first I thought it was somewhere near the entrance to Undead Typhon fight, or somewhere near the passage to the underworld, but it's none of these. The correct place is somewhere near the entrance of Hade's core domain, Fields of the Diadochi. "Sailor to Siren" may refers to Orpheus, son of Apollo. So the place to find the last piece is in the Cave of Apollo. Another explanation might be that both sailor to siren and moth to fire are tragedy, which indicates Sophocles, a famous ancient Greek tragedian. There is a small area called Academy of Sophocles near Fields of the Diadochi.
Anyway we find the place, and the door is also locked. The hint is "Artemis is known to have a good influence on her twin.". Luckily near the Cave of Apollo is Cave of Artemis. Go into that cave, and find a secret lever. Push it and the door in the Cave of Apollo is opened.
Backtracked and found the first piece in Rhakotis. :)
(https://i.imgur.com/UXjmPPF.jpg)
ULTRA SPOILER ALERT, DON'T CLICK IT.
Ptolemy&lighthouse -> Alexandria -> Rhakotis.
Poor people -> slum.
Broken walls -> you can break a wall.
So the piece 1 is located at somewhere in Rhakotis Slum, and you can break a wall to find it.
Tao -> Jade Palace in Qiyun Mountain is a famous Taoism temple.
Go to Jade Palace waypoint, the correct way to find Jade Palace is to go lower left, so the opposite way is upper right. Go upper right and you will find the second piece in a cave.
Seashell&Aphrodite -> birth of Aphrodite -> Sea of Marmara (honestly I don't know how these 2 are related but it seems this is the closest explaination) -> Propontis(ancient name of sea of Marmara)
Piece 3 is located in a cave called "Great Hall of Propontis" near Medea Forest.
There is a fountain near the locked door, so apparently it is the key to open it.
Eye sees a path -> eye of the Grey Sisters is used to see the path of the player in main story.
So kill Grey sisters again, pick up the eye, and click the fountain. The door is unlocked.
"Hade's door" is kinda vague. At first I thought it was somewhere near the entrance to Undead Typhon fight, or somewhere near the passage to the underworld, but it's none of these. The correct place is somewhere near the entrance of Hade's core domain, Fields of the Diadochi. "Sailor to Siren" may refers to Orpheus, son of Apollo. So the place to find the last piece is in the Cave of Apollo. Another explanation might be that both sailor to siren and moth to fire are tragedy, which indicates Sophocles, a famous ancient Greek tragedian. There is a small area called Academy of Sophocles near Fields of the Diadochi.
Anyway we find the place, and the door is also locked. The hint is "Artemis is known to have a good influence on her twin.". Luckily near the Cave of Apollo is Cave of Artemis. Go into that cave, and find a secret lever. Push it and the door in the Cave of Apollo is opened.
I'll be honest it would have taken quite some time for me to figure out how to get piece 3. The others are quite easy though.
I really like this update and how it brings value to places already visited:
The first time I visited the Great Hall of Propontis in Immortal Throne, I thought there would be some kind of quest there but it turned out to be just a big dungeon.
And the cave of Apollo was just a regular cave
I've been able to complete the Primrose Passage but have not been able to open the monsters orbs though I cleared everything.