Now that Cynthia has given you the SecretPotion, talk to the Psyduck that have been blocking access to the north half of Route 210. Administer the SecretPotion and the Psyduck will move off. Cynthia will appear and give you the Old Charm, asking you to deliver it to Celestic Town. Tall grass grows rampant throughout this route, preventing the use of your bicycle. This area is a popular place for Ninja Boys to hide. Further north, the grass clears to give rise to thick fog. To ease travel, HM05 (Defog) may be used, although this is not required.
Head north through the large patch of tall grass, but make sure you find all three members of the Ninja Trio and defeat them, as they won't challenge you unless you stand right next to them. Grandma Wilma, a Move Tutor, lives in a house on the northern, foggy stretch of Route 210 although you'll need Rock Climb to reach it. Previously, she lived in a famous city of Dragon Tamers, and is able to teach the move Draco Meteor to any Dragon-type Pokémon with high friendship. Turn west, then head up the stairs and across the first bridge. From there, carry on straight, across two narrow bridges to find the powerful TM30 (Shadow Ball). Backtrack, and head south over the second wide bridge and then follow the path west to Celestic Town.
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
Celestic Town is a tiny town that preserves the history of Sinnoh and the old ways of life. The center of town has a small shrine that dates back to ancient times. This town is the hometown of Cynthia's family. Although there is no Poké Mart in the town, an elderly couple run a shop out of their house. A man standing in the shop gives away three pairs of glasses to you depending on the time of day. He gives away Choice Specs in the morning, BlackGlasses during the day, and Wise Glasses at night. The Choice Specs powers up the holder's Special moves by 1.5 times, so be sure to take them if you have any special attacking Pokémon.
Next to the Pokémon Center is Cynthia's grandmother. Talk to her and she'll tell you about the Galactic Grunt guarding the entrance to the ruins, so head down the stairs and battle the Grunt at the north end of town.
Trainers with a Vs. Seeker by their names, when alerted for a rematch using the item, may use higher-level Pokémon.
After the battle, Cynthia's grandmother will thank you, and you'll give her the Old Charm. Head inside the ruins and examine the mural at the back of the room depicting Azelf, Uxie, and Mesprit. Team Galactic's Boss Cyrus will show up, interested in the old Sinnoh legends, and after he and Cynthia's grandmother exchange their views on the current state of the world, you'll battle him.
This battle certainly shouldn't be the hardest you've yet had. Cyrus's Sneasel, although fast, has low defensive stats. A Fighting-type move is pretty much guaranteed to take it out in one hit. It's worth noting that Cyrus's entire team is weak to Rock-type moves as well.
After the battle, Cyrus will disappear in a flash and you'll be rewarded HM03 (Surf) by Cynthia's grandmother. Once you leave the ruins, you'll meet up with Cynthia, who heard what happened and now understands that Team Galactic is more dangerous than she initially thought. She'll mention there is a library in Canalave City with books detailing Sinnoh's history, west of Jubilife City. Since it is the location of your next Gym Battle, you will need to head there eventually.
Now that you can use Surf (optional)
Now that have the option to Surf in the field, let's collect some items and battle some trainers around the region.
Starting from the bridge near the entrance to Route 205's south half, Surf on the river northwest and eventually you'll reach Fuego Ironworks. Get off at the northern bank of the river. It's worth noting that outside of the Ironworks, you can find wild Magnemite.
Inside Fuego Ironworks your objective is getting to the boiler in the center, where the owner Mr. Fuego is. You will need to use the spin tiles to reach him. First head into the direction of the southeastern corner of the Ironworks at your own pace, but avoid the tile near Mr. Fuego as that one will take you through another tile that will cause you to start over. After accessing the (↓) tile in the southeastern area you will see three (←) in a line that lead to a larger patch of tiles. The northernmost (←) is the correct one to use and will get you to the area just to the right of the entrance to the boiler place.
Stars for Shards
Mr. Fuego will give you a Star Piece when you first meet him. From now on, you can trade a Star Piece for one of all four different-colored Shards.
On Route 213, use Surf south of Dr. Footstep's house and follow the rock wall eastward. Eventually, you will find a narrow passage to a patch of sea that contains most of the trainers and a few items. South of that is another passage leading to Swimmer Shetlin, a Big Pearl, and a Max Revive. Whenever you visit a small island, be sure to use the Dowsing Machine on your Pokétch to find more items.