Coconut crab is apparently rare item only obtained from fishing and capsule balls. And for gods you don't need impression (unless you want to romance then), you need faith which is obtainable by offering food/meat/corpse/items on their altars.
It is almost imperative to get and keep at least 10 cursed scrolls of lesser material in case you found an unclaimed altar in nefias so you can try change it into Cloth Altar, which enables you to do offerings on the go. Really, really handy for farming faith coupled with the dragon dungeon, since dragons drop heavy corpse. Don't forget to fireproof it, though, since cloth burns if you get hit by fire attacks.
Once you're rich enough to have a ton of Scrolls of High Material you can try to change it into ether instead; keeping ether items inside your inventory won't trigger the corruption effect, only equipping it, and ether are resistant to all effect so you don't need to fireproof/acidproof it.