RPG Insanity

Long time user of the site and finally registered (took me long enough). I really love Kemcos games and this one I love some of the mechanics of it.

But onto my question.  I came across a door under the arena I cannot access.  It states to, " Step away from the door or suffer the consequences.  But if you really want in, watch your timing."  Anyone know how to get in?

I am in the volcano on expert( the only ode I ever play), and my party is level 48.

Am I just too early to access it?

I believe this is the post-game arena (where you already finished the Normal Ending and is after the True Ending).

But I might be wrong and it might be just some timed puzzle dungeon.

 

Also: Welcome to RPG Insanity! \o/

Thanks Jesusalva, that's what I was thinking, but was not 100% sure.