He is a Pixelated humanoid that is black and white sun,a blue glowing eye like sans,bloody eyes,and empty eyes,and a open grin.
Upon this disaster spawning he will in idle until 5 seconds he will chase the player.He can go through wall and anything and the glitch brick will prevent you from seeing this disaster.
Black Sun is in the game called Doom Exe. If you look at his appearance its like minecraft and your correct he is in a flat land with flat trees and there is only 1 tree that is big and is not a flat tree it is a 3d tree.
When he is in idle make sure to run away as far away from him and be in a wide area.Another method is to not take sharp corners because he can take short cuts due to this disaster can go through anything.