On Glaseado Mountain, you will find the Montenevera Gym, led by Ghost-type trainer Ryme.
How to Reach Montenevera Gym
Go along the path that goes northeast from Medali, then after you cross the bridge over the river, turn right at the sign. The path will split again, but you can go either direction. When you reach the snowy mountain area, you can stop at the Pokémon Center, then go northeast from that Pokémon Center and the path will lead you to Montenevera.
Visit the Gym
If you have five Gym Badges already, there will be a cutscene where Mr. Jacq will give you a Lucky Egg, which increases the Exp. that the holder earns.
Talk to the person behind the front desk in the Montenevera Gym to start the Gym Test. Then go outside and go south to the stage. Talk to the person in front of the stage to start the test. You will need to do three Double Battles in a row to pass the test.
First, you will battle Gym Trainer Tas, who has a level 40 Greavard and a level 40 Shuppet. You get 5600 Pokédollars for winning.
Your Pokémon will be healed up, and then you will battle Gym Trainer Lani, who has a level 40 Misdreavus and a level 40 Haunter. You get 5600 Pokédollars for winning.
Your Pokémon will be healed up, and then you will battle Gym Trainer MC Sledge, who has a level 40 Drifblim and a level 40 Sableye. You get 5600 Pokédollars for winning.
Afterward, heal up at the Pokémon Center, then go back into the Gym and talk to the Gym Staffer behind the front desk. If you're ready to battle Ryme, say Yes.
Ghost Gym Leader Ryme, the MC of RIP
After a cutscene, the battle will begin. Throughout the battle, the crowd's cheers will boost the stats of your Pokémon and Ryme's Pokémon. You will have a double battle against Ryme, who has a level 41 Mimikyu, a level 41 Banette, a level 41 Houndstone, and a level 42 Toxtricity that she Terastallizes with Tera Type Ghost. You get 7560 Pokédollars for winning.
You will get a Gym Badge. Check the Gym Badge Effects page to see the level of Pokémon that will listen to you and be easier to catch, or open the Map App or Pokédex App and press X, then select Profile, then press A to see the effects of your current badges.
You also get a TM114 Shadow Ball.
A new Gym Badge means new sandwich recipes. Be sure to stop by any Every Wich Way and talk to the person in front of the counter to learn some new recipes.