The road to Celestic Town, north of Solaceon Town, can only be accessed after you've gotten the SecretPotion from Cynthia after chasing down the Galactic goon and you'll need to have a Pokemon with Defog in order to make your way through the northern part of Route 210 (it's not necessary, but highly recommended). New in Solaceon Town, you'll have to fight against a Team Galactic Grunt and the Boss of Team Galactic himself!