Random..."Thing" Found On My Server

So, I walking around my spawn and I saw this weird thing in the sky and took a journey up it and found this.

It's the creepiest thing ever and I have no clue what it is or where it came from but its there. It isn't even like blocks. Its "not real" so I can just walk on through it. If anyone knows anything about this, please fill me in on this mysterious creation.

 

Someone could have possibly summoned a bunch of entities together.

 

This is the result of using Holograms in your server. What you are seeing is an inverted Horse who's feet can be found in the sky. Some forms of seeing this is by random flashing squares high in the sky or random giant Horse feet in the sky.

Some plugins don't cleanly handle holograms and random Horses and WitherSkulls are left around your world.

 

Thanks Broski! I was so confusled

 

If your using Holograpic Displays update it to a better version. But make sure if your going to update it use the correct "MC VERSION".