Endgame Adventure Dungeons (High-Risk, High-Reward Exploration)

I have an idea for a new endgame system in Minecraft. After players beat the game, motivation often drops because there are no meaningful rewards left, especially for people who enjoy mega builds. Some materials simply cannot be farmed efficiently. My idea is to introduce large endgame dungeons that work as high-risk, high-reward challenges.

Far away from the main End island (or through a special portal), players can enter unique dungeons that must be completed in one go: once you decide to continue, there is no way back until you finish or fail. To prevent cheesing, the dungeon would be played in Adventure Mode or with Mining Fatigue X. Inside, players face combat, traps, puzzles, and Zelda-like challenges.

At the start, you choose your reward type: for example a large amount of quartz, copper, terracotta, concrete, or even diamonds or netherite for the hardest dungeons. The reward quantity depends on the material. This gives players a real reason to explore again, even when they already have everything, because these are the materials you actually need for big building projects.

Optional idea: some dungeons could reward rare decorative blocks or unique variants.
This system would make late-game exploration exciting again and support builders without breaking the Survival balance.