You’ve beaten the Elite Four. You’ve taken down Cynthia—which, let’s be honest, probably took a few tries because that Garchomp is an absolute nightmare. The credits roll, you feel like a champion, and then you realize you’re only halfway done. See, the real game starts when you unlock the Pokemon Brilliant Diamond National Pokedex, and if you don’t know exactly how the encounter system works, you’re going to spend hours running in circles through the tall grass for nothing.
It’s a grind. No way around it.
But it’s a specific kind of grind that requires you to actually use your brain instead of just mashing the A button. Most people think they have to catch every single creature in the Sinnoh region to move on. They don't. That is a massive misconception that keeps players stuck in the post-game limbo for way longer than necessary. You just need to see them.
Why the Pokemon Brilliant Diamond National Pokedex is the real endgame
In the original 2006 versions, the National Dex was a badge of honor. In the remakes, it’s basically the key to the entire kingdom. Without it, you are locked out of the Battle Zone, the Poke Radar, and about half of the legendary encounters that actually make the game worth playing in 2026.
To get your hands on it, you need to register all 150 Pokemon in the Sinnoh Dex.
Wait. 151?
Technically, Manaphy is number 151, but the game is actually somewhat forgiving here. You only need the first 150. This means seeing everything from Turtwig to Palkia. If you’ve been playing naturally, fighting every trainer on every route, you should be sitting at around 130 to 140 by the time you're Hall of Fame material.
The problem is those last ten. There is always a handful of elusive monsters that no random youngster on Route 202 is going to show you.
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The Drifloon problem and other roadblocks
If you missed the Drifloon at Valley Windworks on a Friday, you’re stuck waiting. Or you can mess with your Switch system clock, but Nintendo’s internal anti-cheat often freezes time-based events for 24 hours if it detects a manual jump. It’s better to just wait for Friday. Honestly, just set a reminder on your phone.
Then there’s the infamous Lumineon and Finneon situation. If you didn't pick up the Good Rod and spend some time fishing on the routes heading toward Sunyshore City, you're going to have a blank spot in your Pokedex. Go find a Swimmer. They almost always have the fish.
But the biggest hurdle? It's usually the "other" box legendary. If you’re playing Brilliant Diamond, you have Dialgia. You don't have Palkia. You might think you need to find someone to trade with, but the developers actually threw us a bone here. Head to Celestic Town. Talk to Cynthia’s grandmother in the large house at the top of the village. She will show you a book containing the legend of the opposite version's dragon. Boom. Seen. Registered.
Unlocking the National Dex: The actual process
Once that counter hits 150, fly to Sandgem Town. Talk to Professor Rowan. While you're chatting, Professor Oak—the legend himself—will stroll in like he owns the place. He’s the one who actually upgrades your device to the Pokemon Brilliant Diamond National Pokedex.
Suddenly, the world gets bigger.
You get the Poke Radar. This tool is the holy grail for shiny hunters, but it’s also how you find non-Sinnoh species in the wild. You also get access to the Fight Area via the ferry in Snowpoint City. If you try to go there before getting the National Dex, the guy at the docks will basically tell you to beat it.
What changes in the Grand Underground?
This is where the game actually gets good. The Grand Underground is arguably the best feature of the remakes, but it's nerfed until you get that National upgrade. Once Oak gives you the nod, the "rare" spawns in the hideaways shift.
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You start seeing starters from other regions. You’ll see Charmander. You'll see Totodile. You'll see the weird, high-level stuff that makes competitive team building actually viable.
The statues in your secret base matter more now, too. If you place a lot of Fire-type statues, you increase the odds of seeing those newly unlocked National Dex Fire types in the magma rooms. It’s not a 100% guarantee, but it tilts the RNG in your favor.
Common mistakes people make during the hunt
Most players burn out because they think they need to evolve everything.
Don't do that.
If you need a Blissey for the dex entry, don't spend three hours grinding friendship with a Chansey. Go find a trainer who has one. There are trainers in the Victory Road tunnels and the routes surrounding the Pokemon League who carry the fully evolved forms of the rare babies.
Another huge mistake? Ignoring the honey trees. Munchlax is a nightmare to find via honey—it’s a 1% spawn rate on "munchlax trees" which are randomly assigned to your trainer ID. It’s a bad system. Don't waste your time slathering honey for weeks. Instead, just go to the Grand Underground. Munchlax spawns in the spacious caves once you have the right progression.
The Ramanas Park factor
Once the Pokemon Brilliant Diamond National Pokedex is active, Ramanas Park replaces the old Pal Park. This is where you trade in "Slates" (which you buy with Mysterious Shards found while mining) to fight and catch Legendaries like Mewtwo, Rayquaza, and the Johto beasts.
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It is a massive resource sink.
You will spend hours digging in the walls. You'll find plenty of spheres and fossils, but those Mysterious Shards are rare. Pro tip: Mine in the Grand Underground while you're online. When the "Diglett Bonus" hits 40/40, your chances of finding rare items like shards skyrocket for a few minutes.
Navigating the post-dex world
So, you have the Dex. What now?
First, go get the Heatran event started at Stark Mountain. It's a long trek, and you’ll need a Pokémon with Strength and Rock Smash. It feels like old-school Pokémon—no hand-holding, just a confusing cave and a legendary waiting at the end.
Second, go to the Spring Path. This area only opens up after the National Dex is yours. It leads to Sendoff Spring and Turnback Cave, which is the home of Giratina. It’s a puzzle room where you have to clear pillars before passing through 30 rooms. If you mess up, you start over. It's frustrating, but catching Giratina is the unofficial "final" boss of the collection journey.
Actionable steps for your Pokedex completion
If you are currently staring at a Pokedex with 142 entries and no idea where the rest are, do this:
- Check your fishing spots. Most people miss Barboach and Whiscash. Use the Super Rod in the ponds in Mt. Coronet.
- Talk to every NPC in Celestic Town. If you haven't seen the other box legendary, Cynthia's grandmother is the only way to do it without trading.
- Visit the Battle Tower. Even if you don't like competitive play, just seeing the Pokemon in the opening rounds can sometimes fill those pesky "seen" slots.
- Go to the Backlot's Mansion. The Trophy Garden has a rotating daily Pokemon. Talk to Mr. Backlot every day; he’ll tell you which rare creature (like Eevee or Porygon) has "migrated" to his garden.
- Use the Map's "Registered" feature. Open your town map and look at the routes. If a route shows a Poke Ball icon next to it, you've caught everything there. If it's missing, there's a Sinnoh Dex entry waiting for you in the grass.
Getting the Pokemon Brilliant Diamond National Pokedex is less about the destination and more about unlocking the actual freedom to play the game how you want. It turns a linear RPG into a sprawling collector's paradise. Just remember to bring plenty of Ultra Balls and a Pokemon with False Swipe—you're going to need them.