Closed off when you first find it, Clay Tunnel only opens up in Pokémon Black 2 and White 2 once you've defeated the Champion and entered the Hall of Fame. Once that happens you can gain access to Clay Tunnel from three different points in the west of Unova, the easiest of which is via the tunnel entrance in the north of Driftveil City. This is where we'll begin our spelunking expedition.
Clay Tunnel Pokémon
- Basculin - Common, Surfing / Whirlpool, All Seasons
- Boldore - Common, Walking, All Seasons
- Durant - Uncommon, Walking, All Seasons
- Excadrill - Common, Dust Cloud, All Seasons
- Lairon - Rare, Walking, All Seasons
- Nosepass - Rare, Walking, All Seasons
- Onix - Rare, Walking / Dust Cloud, All Seasons
- Steelix - Rare, Dust Cloud, All Seasons
- Woobat - Rare, Walking All Seasons
Clay Tunnel - Driftveil City
Hiker Teppei
- Aron, level 61
- Mawile, level 61
Reward: 1,952 P
Northeast of Teppei you'll see a Worker, though he's not here to battle. Speak to him and he'll offer to send you on a mine cart ride. If you accept he'll take you to the section of Clay Tunnel adjacent to Mistralton Cave. We'll come back to this guy and his mine cart momentarily.
Head back to Teppei and follow the tracks north. Check the southwest corner of the tunnel as you turn north to find a Blue Shard attached to a rock. Continue north and you'll soon run into a patrolling trainer. In the pit to the right of the trainer you'll find a hidden Full Heal.
Worker Morgann
- Sableye, level 61
- Dugtrio, level 61
Reward: 2,440 P
There's more to see in this section of Clay Tunnel, but thanks to some strategic hole placement you can't get at any of it right now. Hop onto the mine cart and make the trip to the Mistralton Cave portion of Clay Tunnel.
Clay Tunnel - Mistralton Cave
When you pop out into this section of Clay Tunnel you'll see a boulder you can push with Strength. Nudge it to the left to create a path to the west. The rest of this area is pretty open-ended if a member of your team knows Surf - which will allow you to get to a small island with a Steel Gem attached to a rock - but we'll stick with doing a clockwise course around the tunnel. Head south to find a Red Shard and a trainer.
Hiker Manuel
- Swoobat, level 61
- Golem, level 61
Reward: 1,952 P
West of Manuel you'll find a boulder. Push into the hole to the south and you'll find a PP Up and a Nugget on the other side. Northeast of the boulder, hidden in a rock by the water, is a Water Stone. North of the boulder, patrolling the tracks, is another trainer who's waiting to fight.
Worker Herman
- Diglett, level 61
- Machamp, level 61
Reward: 2,440 P
Continue past Herman and you'll find a third trainer, waiting by the tracks. To the left of this trainer you'll find the exit to Mistralton Cave. North of the trainer you'll find an exit to the Twist Mountain section of Clay Tunnel. We explored Mistralton Cave a long time ago, so we'll head north to Twist Mountain after trouncing the Worker.
Worker Paul
- Excadrill, level 60
- Nidoking, level 60
- Rhydon, level 60
Reward: 2,400 P
Clay Tunnel - Twist Mountain
You'll appear in the south end of this section of Clay Tunnel. There's a trainer patrolling a short walk to the north. Southwest of the trainer, down a short side tunnel, you'll find a Metal Coat.
Pokémon Ranger Maxwell
- Forrestress, level 62
- Crustle, level 62
- Armaldo, level 62
Reward: 3,720 P, Lum Berry
To the northwest you'll find a patch of water, and beside it is a trainer on guard. You can fight or avoid him by Surfing.
Worker Leo
- Graveler, level 60
- Onix, level 60
- Steelix, level 60
Reward: 2,400 P
Further north down the tracks is another trainer, as well as a Max Revive. Further north of him is, yes, another trainer, though it's the last one you'll face in Clay Tunnel. Almost done.
Worker Brand
- Graveler, level 60
- Onix, level 60
- Golem, level 60
Reward: 2,400 P
Pokémon Ranger Katie
- Ferrothorn, level 62
- Carnivine, level 62
- Cradily, level 62
Reward: 3,720 P, Lum Berry
To the far north of Katie you'll find the entrance to the bowels of Twist Mountain, another area that you can't access until you've become the Champion of Unova. It's possible this is your first trip to Twist Mountain - though it's also possible you've been through this area before, as Twist Mountain, like Clay Tunnel, has a few entrances. We'll explore Twist Mountain in another article, from a more accessible entrance.
Also in the north is a mine cart that you can ride to another section of Clay Tunnel. Hop aboard and you'll jump off just north two boulders that you can push into holes. Push the southern one into place first and you'll create a path back to the Driftveil City entrance. This will also allow you to get at a Rare Bone, further south in the pit. Pushing the boulder to your right will let you get at a Green Shard, as well as another mine cart, which takes you to yet another mine cart.
At the end of this sequence you'll wind up on the east side of the Twist Mountain portion of Clay Tunnel. Surf north and you'll find an Iron in a rock, as well as a rock-pushing, mine cart-riding path that leads to the northeast end of the Twist Mountain passage. Push the rock to your left into place to bridge the two halves of this area, then head north. There's a Big Nugget tucked into a rock, as well as another tunnel to your right.
Underground Ruins
Your final stop in Clay Tunnel is the Underground Ruins. Seemingly empty at first glance, the Ruins are the hiding place of the three Legendary Titans from the third generation of Pokémon: Regirock, Registeel and Regice. Each Pokémon is found behind the heavy door in the north, though you need to do something special to make each of the Titans appear:
- To make Regirock appear you need to stand in the middle of the double-circled glyph in the middle of the floor, then walk six steps south and nine steps east. Hit the A button and you'll find a switch at your feet. Enter the door once the glyph is red, then slip past the rocks to the right or left of you and head north. Regirock is waiting. Confronting Regirock will earn you the Iron Key (Black 2) or the Iceberg Key (White 2), which you can pass on to other players with the opposite version of the game.
- To make Registeel or Regice appear you need to head back to the main chamber of the Underground Ruins. To use the key of choice, go out to the main menu of the game, choose Unova Link, then Key System, then Mystery Door. Here you can choose where the door leads, and which Pokémon you'll encounter on the other side. You can only get one of the keys in your current game, so you'll need someone else with the other version of Pokémon Black 2 and White 2 to complete your collection of Regis.