The Ancient Ruins: Rare Deep Dark Structure with a Summonable Smoke Boss

We need a ultra-rare endgame challenge hidden deeper than Ancient Cities. I propose "The Lost Ruins," a new underground structure with unique boss mechanics.Generation & Exploration: This structure spawns exclusively deep beneath giant cloud-piercing mountain ranges bordering Savanna biomes. It consists of scattered ruined buildings, long corridors, and large squares filled with valuable loot. Crucially, there are no regular Sculk Shriekers here, meaning the Warden cannot naturally spawn, allowing for peaceful exploration of the main ruins.The Ancient Artifacts & The Warden: Scattered beneath smaller underground hills near the ruins, players can find Ancient Monuments. Here, you can use a Brush on Suspicious Gravel for rare archaeology loot. However, this outer area is dangerous—Sculk Shriekers are active here, so you must watch out for the Warden!The Summonable Smoke Boss: In a massive open plaza inside the ruins, there is a brand new type of special Shrieker block. The player chooses when to start the battle. Once activated, the new Boss Mob spawns with a Wither-like charge-up animation, crawling out of pure smoke. It creates a protective smoke shield around itself, moves incredibly fast, and hits with massive, crushing melee blows. Defeating this boss rewards players with extremely valuable, exclusive endgame loot!