There's a coffin in deep of the underworld, somehow you can see it far away when you're searching for the 7 sins (technically 6 because pride is an asshole), i saw it but i tend to ignore it, because running short of revives and full restore, kinda lazy to run all the way back to the beginning just for shopping, and i regret i didn't go check for it :( that seems like the only chance to check, or else you won't be getting dakrai and cresselia event trigger, that's my current situation, might wanna restart the whole game just to get to play the event.