End Biome - Treasure

I noticed that sometimes endermen take blocks from the overworld and just leave, but there's no place to find the block they took.

What if there was a biome or structure in the end entirely out of stolen overworld blocks? Just a giant pile or even a mountain of grass, sand, pumpkins and TNT.

There could even be a feature that if you mine any blocks in that biome all nearby endermen would get angry.

It would add a lot of hidden story as to why they take blocks in the first place, a lot like the secret rooms hidden under igloos and how they teach you to cure zombie villagers.