Weird structure and noise

This bug was found by me in one of my most favourite seeds..

Seed:- sky block

A weird structure which looked like a piece from the nether spawned near the village close to spawn point. .

Also a creepy noise like what came from end portals was present at all times..

There was also a very scary music going on near this area when underground at midnight in the game.

I don't know what this is.