Just a heads up, the volcano tab in the walkthrough is missing the secret Cat Witch (unsure of actual name) enemy you get via going past the apple tree at the top. She does a melee combo, then an AOE explosion, then a temptation attack. You capture her via hitting her with hammer 4 times, and you can hit her at least once before the fight fully begins. You can also use Wild Slash iirc, but that takes more time.
edit: Also, Nightmare is still the only one that the x-ray function works on as of v1.05. I'm pretty sure you find it by going to the area directly before Gouro's arena, and double jumping to and over the hill on the other side of the drop down.