Player view is sometimes obstructed by a giant texture plane that appears to be based on a player or mob's head texture, rendering the game very difficult to play.

This occurs whenever a mob wearing armour, such as a zombie or skeleton, is within the player's FOV and within approximately 4 chunks, regardless of whether the mob is hidden by blocks. The glitch texture reflects the light level around the mob, and may glow purple if the mob is wearing enchanted armour.