If you’ve been spending time in the Grand Underground during your playthrough of Pokemon Brilliant Diamond or Shining Pearl, chances are you’ve accumulated a good amount of spheres through digging in the walls. These spheres, which come in different colors and sizes, can be used for a variety of special things.
How To Use Spheres
The main purpose of spheres is currency. You may have noticed some NPC hikers down in the halls of the Underground. Many of these are merchants who will trade you valuable items, such as TMs, for spheres. Some also carry pedestals for you to put statues on in your secret base. Each one has a different niche depending on the Underground area you go to—some sell items while others only trade you spheres.
Hikers can also sell Digger Drills that you need in order to move your secret base around as you travel to different cities. They can trade you spheres for random treasures you find, such as shards and heart scales.
How To Optimize Spheres
Trading items to get spheres may seem counterproductive, but this is actually very necessary. Spheres unlock additional space inside your secret base. The extra space can be purchased from the merchant Hiker in the Underground in Oreburgh City.
Doing this costs a lot of shards, but it’s worth it; this is because more room in your base means you can put more statues there, and the more statues you have of a certain type, the better the chance of that type of Pokemon spawning in the Underground rooms.
A hiker’s stock changes from area to area, so definitely always talk to them to see what they are carrying. The more you travel, the more Underground areas will unlock, so don’t forget to use your Explorer Kit as you get to new towns. Now go dig and collect as many spheres as you can!