Ancient End City

Ancient End City is a vanilla-esque add-on inspired by Minecraft's Ancient Cities & End Cities, it tries to expand on the lore in a deliberetely-vague way, adding new pieces to the puzzle. Who built the End Cities? Where did Chorus Flower come from? – and does it through a new large & detailed structure now findable buried in the End dimension.

The structure is rare and fully underground, usually buried inside large End island bodies. That placement is deliberate: the End is supposed to feel barren and dead, but a lot of End-themed add-ons work against that by filling it with new mobs and colorful blocks, which undercuts the atmosphere the dimension. Ancient End City instead tries to read as something that could pass for a natural end-game drop.

The Story...

Inside, you'll find a long-abandoned settlement of explorers, evidently from the Overworld. Ancient builders?

Most of the buildings along the cavern walls served the colony's daily needs, and several still hold their old supplies, including a holy site with a couple of guranteed Netherite-tier gear.

Among all structures, two of them more than the rest, though, because they have lore implications: Where the Chorus Flower actually came from?

The settlers ran a quarry operation at the heart of their settlement. Inside, they found a sealed sphere of Bedrock, their contraptions show they were trying methods of breaking the bedrock – they evidently succeeded and what was sealed inside became their undoing: the first seeds of the Chorus Flower. They moved the findings into an airlocked, redstone-secured containment chamber, trying to study or contain it safely. It didn't work. The flower broke out, and the overgrowth you'll find spreading through the ruins is the result of their adventures.

It's also likely why their end portal was deliberately broken – a last-ditch attempt to seal the wildly-growing flower away from the Overworld, sacrificing their own way home to do it.

TL;DR The idea underneath it all is a familiar one: an old organism unearthed from where it was sealed away, and a civilization undone by disturbing it. This structure explains the reason Chorus Flower exists in the End at all.

The Loot

The loot here is a bit conventional, but that's offset by the difficulty of finding the structure to begin with.

• Two End Portal Frames are obtainable as loot. One can be used to repair the settlement's broken portal and gives you an alternate way home. The other is yours to keep purely as a trophy.
• Numerous smaller buildings along the cavern walls, each serving its own role in the old colony, some containing Netherite and Enchanted Apple loot, and other useful things! The loot is good enough to incentivize you to risk going to the end and looking for it even after obtaining full Netherite gear!

Finding It

The structure is rare and fully contained in large bodies of end stone, so it won't be visible from outside.

• Creative / Spectator: Fly through the interior of large End islands in spectator mode for a few minutes, you'll eventually come across one! (Note: suddenly teleporting to a new area likely won't give the game enough time to find place to generate the structure, so flying into new chunks slowly gives better odds)
• Survival: Dig into every large End island you find. You have a solid chance of tunneling into one if the island is big enough to contain one.
  

New Blocks

Alongside the structure, Ancient End City adds eight new blocks that expand the Purpur and End Stone block families – each obtainable the same way their vanilla counterparts in other block families are obtained, with no new tools or mechanics required.

End Stone family:

• Polished End Stone – smelt End Stone in a furnace (like regular Stone -> Smooth Stone)
• Chiseled End Stone Bricks – stonecut from End Stone Bricks; carved with an eye motif, in keeping with the chiseled block tradition
• Cracked End Stone Bricks – smelt End Stone Bricks in a furnace
• End Stone Pillar – crafted or stonecut from Polished End Stone; an alternative design counterpart to the Purpur Pillar
  

Purpur family:

• Polished Purpur – smelt Purpur Block in a furnace
• Polished Purpur Bricks – crafted or stonecut from Polished Purpur
• Chiseled Purpur – stonecut from Polished Purpur; carved with a Shulker motif
• Cracked Polished Purpur Bricks – smelt Polished Purpur Bricks in a furnace
  

All new blocks include full PBR texture sets, so they render nicely under both RTX and Vibrant Visuals!
Chiseled variant of Purpur depicts a Shulker face, and Chiseled End Stone depicts an End Eye. My personal favorite out of the new blocks is the End Stone Pillar, which features varying-sized columns with a thick core, which is a spin on what vanilla purpur pillar's texture appears to be!