The Golden Room [1]: Princes?

The Earth ruins or simply Trian Ruin was vast.

However, the exploration of ruins had been going on for centuries. So, humanity more or less knew every area.

Of course, they only knew.

In the early stages, humans were much weaker. Even level 7s were incredibly rare back then.

So, the exploration of ruins took time. It started with the weakest areas and then slowly, but surely, humans have uncovered almost every area with their current strength.

A few decades ago, they hit a ceiling in a sense.

They uncovered everything they could uncover. What they couldn't uncover was beyond their strength.

For instance, the Silver valleys. It was a place covered by a silver barrier all the time.

When a level 9 tried to cross the barrier, they were repulsed. But it wasn't without cost. The level 9 was on the verge of death.

Then, Sovereigns themselves came to explore it. However, it was beyond even their reach.