Area Zero has several secrets that remain hidden until the end of Pokémon Scarlet and Violet The Indigo Disk—and even then, you still might not learn everything. Some elements, like the new Paradox Pokémon Iron Crown, need to be discovered through external research before you can encounter them.
If you have the Violet version, Iron Crown is one of the last Paradox Pokémon you can encounter in the game as it was added through the DLC. But you do need to complete a side mission if you want to find it.
Iron Crown location and how to unlock in Pokémon Scarlet and Violet The Indigo Disk
If you completed The Indigo Disk’s story and are wondering why you can’t encounter Iron Crown in Area Zero yet, you might be looking in the right place too early. You need to talk to Perrin, who is located near the entrance to the Blueberry Academy first, who will task you with catching 200 Pokémon in the Teraium for your Blueberry Pokédex.
This side mission, once completed, will reveal that Perrin somehow has photos showing the locations of the two new version-exclusive Paradox Pokémon. After you see those images, you can head back into Area Zero and begin tracking them down.
Iron Crown is actually easier to find than most other Paradox Pokémon once you know where to look. Simply enter Area Zero and head to the spot where you first appeared alongside your classmates at the very peak of the slopes. Then, walk down the path until you come across a hole blocked off by some fencing in the middle of your way.
Jumping down that hole will take you directly to Iron Crown with no extra effort needed. That is much easier than trying to find Iron Boulder a bit further down the way.