A piece of advice before you go, although it does contain spoilers:
(SPOILER)You should save right outside the atoll and remove Leila's equipment.
I've scoured Pandemonium and managed to find another 8 treasure chests, so my item completion is now at 99% with one treasure to go. I've got four monsters to add to the bestiary (I assume one of them is the final boss), and about three concept sketches (again I assume one is of the final boss).