Level 11 - Really sealed?

[Cruzz]

I'd be willing to bet there's more to this level than just the (obvious) pit drop areas from level 10 and the stairway with the fishy sealed note, but running through level 10 several times I still haven't managed to find any kind of entrance. Anyone mind giving a bit of a hint on where to look?

[Poomermon]

You can get there from level 12. It is main quest related so you can't miss it.

[Cruzz]

Ah, thanks. I actually pretty much cleared 12 and 13 before starting to look back at 11, guess I'll just go plug in the final part then.