You remember that feeling back in 2006. Sitting under a dim lamp, trying to figure out why on earth you couldn’t find a single Fire-type in the entire Sinnoh region besides Chimchar and Ponyta. Fast forward to the Nintendo Switch era, and honestly, not much changed with the Pokemon Brilliant Diamond pokedex. It’s a weirdly specific, often polarizing list of creatures that defines the entire experience of trekking through the snow-heavy peaks of Mt. Coronet.
The Sinnoh region is beautiful. It’s also incredibly stubborn.
When ILCA took the reins from Game Freak to develop these "faithful" remakes, they made a very specific choice. They decided to stick—mostly—to the original 150-strong regional listing. This means if you were hoping for the expanded diversity found in Pokemon Platinum, you were in for a bit of a shock at launch. It’s a restricted list. It forces you to play a certain way, focusing on 151 monsters initially before the world cracks wide open after the Elite Four.
The Initial Grind: Navigating the Sinnoh 151
The Pokemon Brilliant Diamond pokedex starts off feeling pretty intimate. You've got your starters—Turtwig, Chimchar, and Piplup—and the usual early-route suspects like Starly and Bidoof. But the "Sinnoh 151" is famous for its gaps. It’s a historical quirk. Back in the day, the developers at Game Freak were clearly obsessed with the new evolutions for older Pokemon, yet many of those evolutions didn't actually make it into the regional dex until the third "definitive" version of the original games.
In Brilliant Diamond, you are dealing with the classic roster. This means you’ll see a lot of Geodude. Like, a lot.
Completing this first leg of the journey isn't just about catching; it's about seeing. To unlock the National Dex—which is where the real game begins—you don't actually have to own every Pokemon. You just need to encounter them. This is a massive relief for people who don't want to spend three hours hunting for a 1% spawn rate in a patch of grass. If you fight every trainer on every route, you'll naturally fill out the vast majority of the entries.
But there’s always one or two that trip people up. Take Drifloon, for instance.
👉 See also: Walkthrough Final Fantasy X-2: How to Actually Get That 100% Completion
Drifloon is the classic "I missed it" Pokemon. It only appears at the Valley Windworks on Fridays. If you clear out Team Galactic on a Saturday, you’re stuck waiting a week unless you’re willing to mess with your Switch’s system clock—which, fair warning, can sometimes freeze time-based events for 24 hours as a penalty. Then there’s Lumineon. You might find yourself staring at a blank spot in the 130s, wondering where that fish is. Hint: Use a Super Rod on Route 223.
Manaphy and the Mythical Problem
One of the coolest, yet easily missed, additions to the Pokemon Brilliant Diamond pokedex is the inclusion of Manaphy. In the original DS games, getting Manaphy was a nightmare involving the Pokemon Ranger spin-off game. In the remakes, it was initially an early-purchase Mystery Gift. Even if you missed the event, you can still "see" it to complete your dex by visiting the back room of the Pokemon Mansion on Route 212. There’s a book on the desk. Read it, and the entry for Manaphy is yours.
This kind of "hidden in plain sight" detail is what makes Sinnoh feel like a real place with its own lore. It's not just a checklist; it's a scavenger hunt through a region that feels genuinely lived-in.
The Grand Underground: Breaking the Dex
If the standard Pokemon Brilliant Diamond pokedex feels too restrictive, the Grand Underground is the escape valve. This is where the remake differentiates itself from the 2006 originals. In the old days, the Underground was for mining and secret bases. Now? It’s a sprawling ecosystem of "Pokemon Hideaways."
These Hideaways are a game-changer.
You can find Pokemon here that aren't in the "official" Sinnoh 151. Want a Houndoom because you realized Rapidash is the only other Fire-type? Head to the Spacious Cave or the Volcanic Cave. Want an Elekid? It’s down there, too. This effectively creates a "shadow pokedex" that runs parallel to your main journey. It allows for team diversity that simply wasn't possible in the original Diamond and Pearl.
✨ Don't miss: Stick War: Why This Flash Classic Still Dominates Strategy Gaming
The spawns in the Grand Underground scale with your progress. As you earn more badges and unlock new HMs (which are now conveniently handled by a Poketch app rather than wasting move slots), the variety of Pokemon in the caves increases. Once you gain the ability to use Strength or Defog, check back in the caves. You’ll find things you didn't see an hour ago.
Crossing the Finish Line: The National Pokedex
Everything changes once you see No. 150 (Manaphy is 151 and technically optional for the first gate, but good to have). You head back to Sandgem Town, talk to Professor Rowan, and Professor Oak rolls in like a celebrity to upgrade you to the National Dex.
Suddenly, the Pokemon Brilliant Diamond pokedex explodes from 151 entries to 493.
This is the real meat of the game for completionists. The National Dex includes every Pokemon from the first four generations. It unlocks new areas, like the Poke Radar, which lets you hunt for shiny Pokemon and rare species in patches of shaking grass. It also opens up the "Great Marsh" and "Trophy Garden" daily spawns, which are essential for grabbing those elusive Kanto and Johto favorites.
- Poke Radar Exclusives: Tyrogue, Staryu, and the Nidoran lines.
- Swarm Pokemon: Every day, a specific Pokemon will "swarm" a certain route. Talk to Dawn’s sister in Sandgem Town to find out which one. This is how you get favorites like Delibird or snubbull.
- Ramanas Park: This replaces the old Pal Park. It’s the endgame gauntlet where you trade in Slates for encounters with Legendary Pokemon like Mewtwo, Rayquaza, and the Johto beasts or Kanto birds (depending on your version).
Version Exclusives and the Trading Wall
We have to talk about the elephant in the room. You cannot finish the Pokemon Brilliant Diamond pokedex alone. It’s impossible by design. Pokemon is, and always has been, a social experiment in trading.
Brilliant Diamond players get the cool stuff like Dialga, Cranidos, and Murkrow. But you’re never going to see a Shieldon or a Glameow unless you know someone with Shining Pearl.
🔗 Read more: Solitaire Games Free Online Klondike: What Most People Get Wrong
Then you have the trade evolutions. Alakazam, Machamp, Gengar, and Golem. These four are the "Big Four" of frustration. If you don't have a trusted friend, you’re stuck entering global trade rooms and hoping someone doesn't run off with your Haunter. It's a bit archaic, sure, but it maintains that old-school playground vibe that defined the franchise for decades.
The Feebas Nightmare
Is any discussion of a Sinnoh pokedex complete without mentioning Feebas? Probably not.
Feebas is the ultimate test of patience. It lives in Mt. Coronet, in a massive underground lake. It only appears on four specific tiles in that entire lake. Those tiles change every single day. You have to fish on every single square, multiple times, just to find the "lucky" spot. Once you catch it, you have to max out its Beauty stat using Poffins to evolve it into the majestic Milotic.
It’s tedious. It’s grueling. And honestly? It’s one of the most rewarding captures in the game. It’s a badge of honor.
Completing the Dex: Actionable Steps
If you’re serious about finishing the Pokemon Brilliant Diamond pokedex, you need a strategy. Don't just wander around aiming for the tall grass. You'll burn out.
- Battle Every Trainer: This is non-negotiable. Don't skip the hikers or the swimmers. They have the rare evolutions you won't find in the wild until much later. This ensures you "see" the 151 quickly.
- Use the Grand Underground Early: Don't wait for the post-game. Start building a diverse team in the caves as soon as you get the Explorer Kit in Eterna City. It makes the Elite Four much easier if you aren't stuck with a mono-type team.
- Check the Trophy Garden Daily: Mr. Backlot’s mansion is more than just a place to see Manaphy. After you get the National Dex, he’ll start "finding" rare Pokemon in his garden. This is the only way to get Eevee, Porygon, and several babies like Pichu or Happiny in the wild.
- Synchronize Your Clock (Carefully): If you’re hunting Drifloon or waiting for a specific swarm, be mindful of the time. If you must time travel, do it, but accept that some features will lock for a day.
- The Box Legendaries: You’ll catch Dialga as part of the story. To get the Palkia entry in Brilliant Diamond, go to Celestic Town. Talk to the elder (Cynthia’s grandmother) in the large house at the top of the town. She’ll show you a photo of Palkia, which counts as an encounter for your pokedex.
The journey through Sinnoh is a slow burn. It's not the fast-paced, "catch-em-all-in-five-minutes" vibe of the newer mobile-integrated titles. It requires a bit of grit. But when you finally see that certificate from the Game Director in the Hotel Grand Lake, it feels earned.
Maximize your use of the Poke Radar post-game. It’s the most efficient way to chain encounters and find those final missing pieces. Keep your Berries planted and your Poffin pot stirring. The Sinnoh region is waiting, and that Pokedex isn't going to fill itself.