A Pokémon with Infiltrator is able to bypass the opposing Pokémon's walls without the benefit of using Brick Break, enabling its moves to work as if the walls weren't there.
Infiltrator doesn't have an overworld effect.
Pokémon With Infiltrator
Related ThreadsWhere is the Infiltrator? - last post by @ Nov 19, 2017
Can someone tell me where the infiltrator is? - last post by @ Nov 26, 2003