AETuts shared a detailed Unity guide that will explain to you how to set up a Bastion effect.
The video discusses how you can create a shader that changes the size and position of the mesh based on the distance between the player and the mesh. The artist noted that the shader was created using Shader Graph in the LWRP of Unity 2019
You can move your character back and forth, and the shader will automatically change your level's visibility using the position of the character.
You have to agree that the effect looks amazing, and the best thing is that it's quite easy to recreate in Unity. Discuss the tutorial in the comments.