The Montenevera gym can be found in the snowy mountains on the northern end of Paldea in Pokémon Scarlet & Violet. Gyms can be attempted in any order, but it's best to save this gym until your Pokémon are past level 40. Getting to the city alone will be a challenge for those who aren't adequately prepared.
This gym focuses on double battles and can be unique in its concert aesthetic and mechanics. The crowd is watching and reacting to every move, and they offer buffs to whichever side is doing better. This gym can be a quick snowball for whichever side starts off on the right foot.
Warming Up The Crowd
For this gym, the test is to simply warm up the crowd before the gym leader's concert. While this may seem simple at face value, the crowd needs to be warmed up by watching back-to-back double battles. Once these battles have begun, you must complete all three in a row before you can take a break. After each battle, your team will be healed, and for the most part, these battles are a warm-up for yourself for the double battle system.
For each of the three double battles, you will start with your first two Pokémon out and have your entire team available for the battles. These three opponents only have two Pokémon each, meaning you should double up and focus on taking down one or the other on the first turn using both of your own Pokémon. For each Pokémon defeated, the crowd will offer a boost to attack and a special attack to both of your Pokémon or both of the opponents if they take out one of yours.
The crowd will also continue to cheer and offer random boosts to either side. Your first opponent will have a Greavard and Shuppet, both at level 40. Use both of your Pokémon to target one of your opponents with either Dark or Ghost-type attacks. This should ensure you eliminate one right away, ending in a 2v1 for whichever Pokémon is left.
Your second opponent will have Haunter and Misdreavus, both at level 40. Use the same strategy but focus on taking out Haunter first, as it will spam hex and potentially hurt your party more than Misdreavus. Your final opponent will have a Sableye and Drifblim, both at Level 40. Drifblim knows the self-destruct technique and may use it right off the bat. Make sure you have a strong dark or ghost-type waiting in the wings to clean up should your first two Pokémon suddenly get wiped out while Sableye is still fighting.
Gym Leader Ryme
Unlike previous gym leaders, Ryme will be fought in a double battle with the crowd cheering you both on. Ryme will have 4 Pokémon, so taking down one fast for the 2v1 advantage is not as easy. Whichever side takes down an opponent will get the bonus attack and special attack boost from the crowd, which can help you or Ryme snowball this fight, depending on who gets the first KO. The crowd will also give random buffs in other stats to both parties throughout the battle.
Banette - Level 41
Banette is one of the first Pokémon sent out by Ryme. It is purely a ghost type, so focus on it with Dark or Ghost-type attacks with both of your Pokémon to take it out in the first turn. Doing so will quickly cycle to the next Pokémon and begin the first of many of your team's attack buffs from the crowd.
Mimikyu - Level 41
Mimikyu is one of the first Pokémon sent out, but you should be worried about the second. Mimikyu's disguise ability will make the first hit it receives do minor damage. This makes it very difficult to wipe out in the first round, and the added damage buffs should help make the attacks after its disguise is broken take it out quickly. Mimikyu will also use a move that always attacks first, making it a constant annoyance you need to take care of quickly.
Houndstone - Level 41
Houndstone will hit hard and disappear for half of each turn, primarily using an attack that makes it disappear for a turn before attacking, making it invulnerable during this time. Should your original Pokémon still be fighting, the bonuses to their attack stats will help take out Houndstone in one lucky turn. Fighting with Pokémon that aren't buffed may mean one of your own won't make it through due to the sheer damage Houndstone can cause with one attack.
Toxtricity - Level 42
Toxtricity is not usually a ghost-type but will Terastallize into one on its first turn. Toxtricity is naturally a fast-moving Pokémon, and if it's receiving too many buffs from the crowd, it can quickly wipe out the rest of your team. Heal or use tanky Pokémon to stay alive and keep it from getting the damage buffs; from there, focus on it with strong super effective attacks, and it shouldn't take many.
Beating this gym will reward players with TM 114 Shadow Ball. This move is a ghost-type attack that has 80 power, 100 accuracy, and 15 PP. Targets hit by this move may also have their special defense lowered.