All mobs hostile towards iron golems will go to village centers and will attack the air. - It seems like the mobs AI think that there is an iron golem there, when there isn't. - Projectiles will also bounce off the 'invisible' golem too.
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Also can confirm. They attack Village Squares thinking there's an iron golem. When you reload the world, the iron golem spawns.
So the iron golem exists but it's invisible and invulnerable???
Can confirm. This was observed in xisumavoid's snapshot video.