After battling your friends on the Grande Vallée bridge, you reach Snowbelle City, home of the eighth gym.
In the Pokémon Center, you will find Mr. Bonding, who gives you the sixteenth O-Power, PP Restoring Power. This is the second to last O-Power. If you have sixteen O-Powers, go to Lumiose City and increase your style (read the Lumiose City page to learn how to increase your style), then go to the Café Introversion in South Boulevard. If your style is high enough, and if you have fifteen O-Powers, Mr. Bonding will be there, and he'll give you Hatching Power. Keep in mind that you can also reduce hatching time if you have a pokémon with the Flame Body ability in your party next to the egg.
There are two houses north of the pokémon center. In the one on the left, the guy downstairs will teach a move to Keldeo or Meloetta.
In the same house, the battle girl upstairs will give you TM08 Bulk Up.
There is a Move Tutor in the southwest house who will teach the ultimate moves to starter pokémon.
Use your Dowsing Machine in front of the Move Tutor's house to find a hidden X Sp. Atk on the tree to the right of the house.
Slightly northwest of the Move Tutor's house, there is a ramp that you can slide down to a lower area. Go south there to find a Full Restore.
In the northwest house, the girl upstairs (named Punky) will give you a level 50 Bisharp (named Pierce) if you give her a Jigglypuff. You can catch Jigglypuff in some of the next locations that you will visit. I consider this a good trade, because although you can catch Pawniard in Route 15 and the Lost Hotel, it doesn't normally evolve into Bisharp until level 52. If you haven't been training a Pawniard, it's easier to just trade for Punky's Bisharp. However, you might want to take Pierce to the Move Reminder in Dendemille Town to teach it some more attack moves, because its only attack move to start with is Night Slash.
Along the north edge of town, use the Dowsing Machine to find an Icy Rock to the left of a house.
There is a hidden Full Heal on the narrow strip of snow between the Clothing Boutique and the Snowbelle Gym.
When you go to the Snowbelle Gym, there is a guy blocking the door. He says that the gym leader, Wulfric, is in the Winding Woods. Use the southwest exit of town to reach Route 20: Winding Woods.