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How to Make a Secret Base in the Grand Underground in "Pokémon Brilliant Diamond" and "Shining Pearl"

Kain writes video game articles that include tips, tricks, and tutorials. He is especially enthusiastic about horror games.

Secret Bases return in the Pokémon Brilliant Diamond and Shining Pearl remakes. The games are exclusively available on the Nintendo Switch. The original Diamond and Pearl from the Nintendo DS system also had an underground area beneath the Sinnoh region. The remakes have significantly expanded the Grand Underground. It can be accessed relatively early on in the game.

The Grand Underground is a massive and sprawling labyrinth with tunnels, caves, and large rooms that may contain rare items or Pokémon. If you're not sagacious enough, you can easily get lost and confused. Seriously! It's a pretty massive area to explore!

The Grand Underground can be explored solo or with other players. You'll need a Nintendo Switch Online Subscription to play with other people, though. Many different kinds of Pokémon roam freely in this location. There are no random encounters with Pokémon while visiting the Grand Underground. The question marks are large rooms that you have yet to explore.


Building a Secret Base in "Brilliant Diamond" and "Shining Pearl"

You'll need an Explorer Kit to access the Grand Underground. Once you reach Eterna City in the main story, go to the Undergound Man's House. It's right next to the Pokémon Center. The house has a blue door and yellow roof.

Visit the Grand Underground at least once with the Explorer Kit. Return to the old man and speak to him. He asks you to dig up some treasures for him.

Digging for Treasures

While underground, check the map for little spots of yellow light. Press the R button to search for them. Walls that sparkle yellow mean they can be searched. Once you're facing a yellow spot, press the A button to start digging. The game will say the walls are bulging slightly.

You'll be utilizing a pickax and a sledgehammer for digging treasure in Brilliant Diamond and Shining Pearl. The sledgehammer is good for breaking up the large rocks. The pickax is better for the weaker areas in the wall.

Walls will eventually collapse after you repeatably hit them with either the pickax or sledgehammer. A crack at the top of the screen indicates how damaged the wall is before it will collapse. Try to find all the treasure before that happens. It's best to hit the pickaxe around the corners first. Sometimes you can see something shiny that might be blue or red, indicating a treasure behind. Spread your hits across the wall strategically. It's possible to acquire rare items like a Fire Stone, an evolution stone for evolving certain Pokémon.


Digger Drill for Secret Base

Once you've got some Spheres, return to the Underground Man in Eternal City again. He'll reward you with a Digger Drill. The Digger Drill is a tool that is used to create a Secret Base nearly anywhere in the labyrinthine caves. Make sure to remember where you build your Secret Base, for it's easy to get lost in the Grand Underground due to its massive scale. Use the map and take a screenshot.

Placing Statues in Secret Base

Sometimes you'll unearth statues when digging. Statues can be placed inside your Secret Base. They can be placed in different positions. While they serve a decorative purpose, they can also be used to attract certain Pokemon.

Shiny Statues can be obtained if you collect all the orbs that the Diglett and Dugtrio give you. Once 40 orbs are obtained, you'll have a few minutes to dig at spots that are guaranteed to have a rare item or Shiny Statue. The normal Secret Base can hold up to 18 statues if there is enough space. It can be expanded by giving Spheres to one of the hikers.


Catching Pokemon in the Grand Underground

The monumental rooms with question marks are areas where wild Pokémon roam freely. Some Pokémon will be unavailable until the post-game. However, it's still possible to catch rare and unique Pokémon like Scyther, Togepi, and Houndoom. Which ones you encounter is slightly random, but it also depends on what version of the game you have. The large rooms have different colors on your map. Try visiting other locations to discover new species. Scyther, for example, is not available in Shining Pearl. You'll need to trade with other players.

Pokéballs for Catching Pokémon

The Quick Ball, Dusk Ball, and Ultra Ball are good Pokéballs to use in the Grand Underground. The Quick Ball makes it significantly easier to catch Pokémon if you throw it on the first turn. Dusk Balls are good to use at night or inside of caves. Ultra Balls have a better catch rate. If you're having trouble, throw a Timer Ball after 10 turns have passed.


Weaken Pokémon in Battle to Catch Them

Unless you're using a Quick Ball, it's best to weaken a Pokémon before using a Pokéball. Make sure their health is in the yellow or red. Avoid making them faint by using False Swipe, an attack that will leave the target with at least 1 HP. Super Fang may also be useful, as it cuts the targets HP in half.

Paralyze wild Pokémon with moves like Thunder Wave or Nuzzle. Status effects make them easier to catch. However, poison and burns can cause them to faint. Putting a wild Pokémon to sleep with Yawn or Sing can work, but it's an ephemeral effect.

Rare Spawns

Reentering the large rooms in the Grand Underground increases the probability that rare Pokémon will appear. If you don't see anything interesting, simply exit the room and reenter. This can be done an unlimited number of times. Lastly, check for Pokéballs on the ground. Sometimes you'll find TMs or other rare items.


© 2021 David Patrick