Peak Grandmaster Flesh Golem

It was Nero who had found the place; it was underground, dilapidated like the rest except for the gemmed door, which seemed to be in good condition.

Five Grimm Grandmasters are staring at the gemmed door. The door is metallic, but it had thousands of gemmed runes moving around. Every second, these gemmed runes would form a new formation, leaving one scratching their head on the way to solve it.

"Aleigari puzzle," I whispered as I saw the changing runes; this is a very complicated puzzle of a thousand changes category. This means there are a thousand formations, and one will have to solve all of them to clear the puzzle.

Which would take months and some years; most of the rune specialists are not even capable of solving it.

There is one short way to solve it; it is to find the core formation of all thousand formations and solve it. Which is called the central key, and it is not easy to get.