Hello and welcome. I am the Chairman and Creator for the Magma Battle Frontier. I hope you enjoy it. Now, this is what you need to know when battling another Trainer;
All levels are the same level as the highest level in your party. For example, say you entered the Battle Pyramid with these Pokémon;
Wurmple Lv6
Geodude Lv8
Machop Lv7
Then, all opposing trainers' Pokémon are level 8. Now, I realize this may be difficult to work with here, so, all your other Pokémon get elevated to suit. So your team now would be;
Wurmple Lv8
Geodude Lv8
Machop Lv8
However, they don't stay increased outside of the Battle Frontier.
You may not use items in any challenge (except Artisan Cave and Battle Pyramid.) Held items however, may be used.