This is basically the Hogwarts Legacy 100% trophy, because nearly everything in the game rewards you with something that will register in the “Collection.”

The Collection is basically your Field Guide’s progress page, tracking and showing everything you’ve done in Hogwarts Legacy. It shows you every reward for every chest you’ve opened, every Revelio page you’ve discovered and every side quest reward you’ve unlocked. It also shows the enemies you’ve encountered, the wand handles you’ve discovered, the beasts you’ve happened upon and so on. Like I said, absolutely everything.

This will be your post-game content, basically. Once you’ve finished the campaign, all side quests, found every bit of treasure and done every single challenge - as well as finding all the Revelio pages - this trophy will be all yours. And much deserved too!

Just follow the icons on the map when you unfog the area (head to the Floo Flames first) and do everything in your quest log and you’ll start to make a real dent in it. Good luck!

In order to unlock this illusive achievement, you'll have to fill out all 10 categories:
Hogwarts Legacy Collection: All 150 Revelio Pages and where to find them
Hogwarts Legacy Collection: All 140 Conjurations and where to find them
Hogwarts Legacy Collection: All 42 Wand Handles and where to find them
Hogwarts Legacy Collection: All Tools and All Ingredients
Hogwarts Legacy Collection: All 78 Appearances and where to find them
Hogwarts Legacy Collection: All 75 Traits and where to find them
Hogwarts Legacy Collection: All 67 enemies and where to find them
Hogwarts Legacy Collection: All Broom Locations
Hogwarts Legacy Collection: All Beast Locations

And in order to assist with those, we have the following region guides:
Hogwarts Legacy: All The Grand Staircase Collectibles (100%)
Hogwarts Legacy: All Astronomy Wing Collectibles (100%)
Hogwarts Legacy: All Bell Tower Wing Collectibles (100%)
Hogwarts Legacy: All Library Annex Collectibles (100%)
Hogwarts Legacy: All South Wing Collectibles (100%)
Hogwarts Legacy: All Great Hall Collectibles (100%)
Hogwarts Legacy: All Hogsmeade Collectibles (100%)
Hogwarts Legacy: 100% Highlands All Collectibles Region Guide & Maps

And finally, you'll need to get the following collectibles, not found on any maps:
Hogwarts Legacy: All Vivarium Collection Chest Locations
Hogwarts Legacy All Butterflies Locations (Conjuration Collection Chests)