In this tutorial, we’ll create a “See-Through Walls” effect similar to the one that is used quite often by Nintendo on their games. We will replicate the effect in Unreal using a custom stencil buffer and a custom post-processing effect.
https://dev.epicgames.com/community/learning/tutorials/Wvzz/unreal-engine-nintendo-inspired-see-through-walls-effect-in-unreal-5