Not open the door to the Tomb kings. (Final Fantasy 15)

Good afternoon. I know that some of the tomb scene. But I can not find anywhere what.
But the problem is that the cleared Tomb of the Smartest, everywhere on the Internet write that it is free, killed Samurai Aramus 52 level and the entrance to the crypt is closed... And I'm not about round iron, which is unlocked after beating the story, but about the crypt. Maybe there is a place in the story, where are the miracle key? and I came to him... or just a bug?