The Unseen Observer.

v1.7 New:

The Observer now knows your real name. Not your Minecraft name.

Added a written book that may appear in your inventory. We didn't write it.

The Observer has been keeping track of how many times you've died. It will tell you.

Something that looks like you may appear in the distance at night.

First time you see he, you'll get an advancement. "He Found You."

Your inventory may rearrange itself. Nothing is missing. Probably.