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Pokémon Brilliant Diamond and Shining Pearl: Grand Underground guide

We’re deep in the cycle of Pokémon games releasing both new titles as well as remakes of the originals. Newer games, like Pokémon Sword and Shield, have been more controversial among the die-hard Pokémon fans for one reason or another. However, even if the new games no longer satisfy the older fans, the remakes of the first several generations are there to bring the older titles onto your current hardware with plenty of graphical, technical, and mechanical improvements. The latest of which are the Pokémon Brilliant Diamond and Shining Pearl, remakes of Diamond and Pearl for your Nintendo Switch.

Pokémon Brilliant Diamond and Shining Pearl make the Sinnoh region look and play better than ever. One of the most interesting features of these games that we never saw brought back was called the Underground, where you could do a few simple optional activities. In the remake, however, things have been overhauled with new content, turning it into the Grand Underground. Whether you played the originals back in the day or are a brand-new trainer in the Sinnoh region, here’s a full guide on everything you need to know about the Grand Underground in Pokémon Brilliant Diamond and Shining Pearl.

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How to get to the Grand Underground

The first thing you’ll obviously want to know is where the Grand Underground is and how to access it. Thankfully, you can’t miss the required item to reach this area in Pokémon Brilliant Diamond and Shining Pearl. Once you’ve beaten the first gym and thwarted some of Team Galactic’s plans in Floaroma Town, you will pass through Eterna Forest to reach Eterna City. You won’t be able to progress farther than this point until you go into the Underground Man’s House, which is conveniently located right next door to the Pokémon Center.

Once you go inside, just talk to the old man about caving and he’ll provide you with a new Explorer Kit. You’ll be prompted to use it immediately to enter the Grand Underground and find three gems for him. Complete this simple task, turn them in, and he’ll also give you a Digger Drill item, which you’ll need for later. Once you’re free again, you can simply use the Explorer Kit at any time to warp back to the Grand Underground whenever you wish.

What you can do in the Grand Underground

A trainer exploring the Grand Underground in Pokémon Brilliant Diamond and Shining Pearl.

So now that you’ve made it to the Grand Underground, what can you actually do here? Well, there are quite a few reasons to dive deep into these caves, including new ones exclusive to Pokémon Brilliant Diamond and Shining Pearl. There are special rooms that you can find here that are the only places in the game you will find certain rare Pokémon, you can do different mini-games for special items, and you can build your own secret base.

How to set up your secret base

Standing in the secret base full of Pokémon statues.

Let’s start with your secret base. Remember that Digger Drill item the old man gave you? This is what you’ll use to carve out your hidden chamber in the Grand Underground. To set up your hideout, simply approach any way you like and use it to excavate a new room all for yourself. Just be aware that your Digger Drill is a one-time-use item, so if you want to move your secret base somewhere else you’ll need to buy another one from a vendor. In the original game, your base was just a place you could set up some basic decorations that had no real effect, but in Pokémon Brilliant Diamond and Shining Pearl, they have introduced statues, which play a very important part in the Grand Underground ecosystem.

You will need to find these statues first, though. While exploring the Grand Underground, follow your map to the shining spots. Once you’re in the right area, hit R to activate your radar to identify exactly where a treasure is located. This will start a digging mini-game, which we will cover in depth below, where you have the chance at collecting gems, rocks, plates, fossils, evolution stones, and statues.

When you have statues, you can arrange them in your base using a grid. The reason you’ll want to use statues over other decorations, or specific statues over others, is because they will increase your odds of finding different Pokémon types in the different biomes you find in the Grand Underground. Whatever the type of Pokémon statue you place, the better odds you have of encountering more Pokémon of that same type.

Pokémon obviously come in a range of shapes and sizes, so it follows that their statues do as well. That means some will take up more squares in your grid than others, but the larger a statue is, the more it raises your chances of finding a Pokémon of that corresponding type. You’ll want to balance out and maximize your space by mixing in larger and smaller statues to get as much benefit as possible. Later on, you can expand your base to fit more statues too.

Where to find rare Pokémon

Garchomp facing off against Lucario.

The biggest draw for most trainers to start spelunking in the Grand Underground has to be all the rare Pokémon you can find only there. This is the only spot you can find a number of pocket monsters that weren’t in the original games, or only in the Platinum version. To find them, you will need to go to different areas, which are called Pokémon Hideaways, to track them down.

Pokémon Hideaways are all themed differently, with unique Pokémon spawning there related to what type of environment it is. Withing the Grand Underground, the map itself can be separated into six different zones, each one with a mystery room where the new Pokémon live. You can even arrive in zones of your choice based on where you use the Explorer Kit to travel to the Grand Underground since the two maps lay on top of each other. To get to each different zone, you can use your Explorer Kit in these areas:

  • Twinleaf Town
  • Eterna City
  • Celestic Town
  • Snowpoint City
  • Sunyshore City
  • Fight area

Aside from the statue method of boosting different Pokémon spawn rates, you will also encounter more Pokémon in Pokémon Hideaways by getting new HM and completing milestones. To specifically increase your odds of finding Pokémon that are only in Pokémon Brilliant Diamond and Shining Pearl, and not the originals, you will need to complete the Sinnoh Pokédex and unlock the National Pokédex.

Master the dig and Diglett mini-games

Digging items out of the wall.

Finally, there are two mini-game-type activities you will want to master as part of the Grand Underground experience. These are the digging game, where you can get all those rewards we mentioned when talking about statues, and encountering Diglett and Dugtrios.

Let’s start with the digging mini-game since it’s much more complex and has a range of rewards to earn. While exploring, you will find the dig spots, just like in the tutorial mission where you first got the Explorer Kit, those telltale sparkles on your map. Approach them and interact to begin the digging game, opening up a new grid. Your goal is to recover all, or as many, of the hidden items as possible using either the hammer or pickaxe tools. Before you begin, the game will tell you how many items there are to find as well. However, you only have a certain number of total swings before the area you’re working in caves in and kicks you out as indicated by a growing crack along the top of the screen. Hammer swings will cause it to grow faster than the pickaxe, so be careful swinging that thing around too much.

The hammer tool is best used first, since it is more blunt and powerful, but once you locate a treasure you will want to switch over to using the pickaxe to avoid breaking the prize. Once the cave inevitably collapses, you will get a full recap of all the goodies you managed to uncover, and any treasure chests you found will pop open for you to reveal their loot. All of it will be placed in your inventory. Remember to take your gems to the different vendors for more Grand Underground items like podiums you can place your statues on.

Running through the Grand Underground.

Last up, keep your eyes peeled for Diglett and Dugtrios while exploring the caves. As soon as you enter the Grand Underground, you’re likely to notice a meter underneath your map with a counter starting at 0 that maxes out at 40. By finding either a Diglett or Dugtrio, which appear at intersections on the map, you will cause them to “run” away and leave behind a trail of pink sparkles. By collecting these sparkles, you will build up that meter below your map, with a Diglett raising it by 1 and Dugtrio by 3.

When you eventually reach a full bar with 40 points, a few awesome things happen. First is that your odds of finding a shiny Pokémon in any of the Pokémon Hideaways will go from 1 in 4,096 all the way down to 1 in 2,048. That won’t make it a guarantee you’ll get a shiny one, but those odds are still way better than normal. Second is that you will also have better chances of finding the special green sparkling statues in the digging mini-game.

Just know that these effects are not permanent. Once the bar is full, you only have four minutes to capitalize on these increased odds before you will need to build it back up again, so make it count.

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