This character wears white with darkened spots all over, and a completely black face with red eyes. It is speculated to be a being that was either the creation of Herobrine, the creator of Herobrine, or a separate being that is potentially as powerful as Herobrine and possibly his enemy or ally, however, this has not been decided yet.
"Entity 303 (Short)" Edit
This takes place in a random survival world in Minecraft. As the person walks out of the cave and into the woods, he meets Entity 303 before mysteriously experiencing nausea and weird visions.