how far away can monsters spawn in terraria
Spawn Zone. Enemies spawn in a rectangle around you, no matter your resolution. They're always off screen unless you're using a resolution-increasing mod to go beyond 1920x1080, it's why we don't see monsters appear out of thin air. The screen area (no spawn zone) is 62 tiles to the left and right of the player. 35 tiles up and down from the player. Monsters can spawn in an area 22 tiles to the left and right of this, and 12 tiles up and down - roughly. This means there's room for error, but it's also not a very large zone where spawns actually take place. If monsters are too far outside the spawn zone, they despawn.