Deep within Mount Fuji lies a hellish, tainted world, where the demented Infernal Priest Dagra Dai invokes dark ceremonies and incantations to resurrect the Archfiend. Every heartbeat of the fetal overlord rumbles like an omen of death for the human race. Ryu enters the Underworld, where no human has ever set foot before. He does not yet realize that he is in the land of the dead, home to those who have shuffled off this mortal coil.
Part 1: Underneath the Mountain
Immediately to your right as you begin the level is a Muramasa Statue. Stock up if you need to and continue up the path. A swarm of Bat Fiends will attack you, so be careful not to progress to far up the path or you will be swarmed or pinned down by fireball attacks. Run and dash to get past the fireballs along the path ahead. Heading up the cliff, there is a corpse holding a Devil Way Mushroom, and farther along is a Dragon Statue. Save/heal here, as you have a boss fight coming up soon. Head up to the next area.
Boss: Two Armadillos
This boss is the same as before, but now there are two of them. Immediately attack the head of the front one with Incendiary Shurikens over and over again. With a little luck, you will down him before he gets to breathe. If he gets angry, avoid his devastating meteor attacks. Use the same procedure with the second one. When each one falls, finish them by attacking their head with Y and then quickly back away and block to avoid the explosion that accompanies their death.
Part 2: Lake of Fire
If you took a beating in that last battle, you will have to backtrack to the shop to restock. You won't see another one ahead for a long time and this level can eat healing items if you are not careful. Head to the end of the large area and down the cliff for a cutscene. After the cutscene, there is a chest just ahead of you and left. Open it for an Herb of Spiritual Life. Continue up the path. Kill the group of Purple Fiends ahead and look in the lava just under the bridge for a chest containing some Blue Essence. Farther back and to the right in the lava is a corpse with a Devil Way Mushroom. Continue down the path and slide down a hill to a large, open area. Here, you will be attacked by Dog Fiends. They are a bit like the Zombie Dogs that you fought earlier, but slightly tougher. Continue ahead to be ambushed by another wave of Bat Fiends. There is a chest to there right, before the Dragon Statue that contains several Red Essences. Use the Dragon Statue here and continue up the path.
In the area just past the Dragon Statue, you will be attacked by a group of Bat Fiends and some new Dragon Fiends. The new fiends are almost identical in attack style to the Bat Fiends, with the exception of their roll attack. Continue along the path ahead and drop down to the platform below to land on some rocks in a fiery lake. Jump to the right and search the corpse here for a Devil Way Mushroom, fighting off the Fiery Ghost Fish that attack you here. The center rocks have a corpse that contains arrows, and the other corpse in the room holds a Grains of Spiritual Life. When you have collected them all, head to the center platform for a boss battle.
Boss: Greater Fiend Zedonius Redux
Zedonius again. Most of his attacks are the same. He's added a fire beam and fire wall attack and now you have the lava to watch out for. Avoid getting knocked in and follow the same strategy as before. He will block your flying swallow attacks, so try for ground attacks. I recommend the Eclipse Scythe's spinning Y attack. When he dies, examine the item on the ground to receive the Heart of Malevolent Flame.
Part 3: A Subterranean Forest, an Underground Desert
Before heading into the cave ahead of the platform that you fought Zedonius on, be very careful. Use the arrows you just picked up to kill the explosive Squids in the water. Those, in combination with the lava, will almost instantly kill you - and you don't want to reload in front of Zedonius again, do you? Water run into the cave and use the Dragon Statue to save/heal. Search the chest to your left to obtain an Herb of Spiritual Life and then head out of the cave, into a forest. There is a Muramasa shop ahead. After stocking up, proceed ahead. The Cyborg Fiends that attack here are very difficult. Their attacks are fast and damaging, they can shoot lightning from a distance and their grab attack is destructive. They are very allergic to Art of Inferno and to Flying Swallow attacks from your True Dragon Sword. After you defeat them, press ahead. There is another wave of Cyborg Fiends here. Kill them off and look toward the tree to the left of the exit to the forest for a chest containing an Herb of Spiritual Life. Exit the forest. In the desert area ahead, you will trigger a cutscene.
Boss: Greater Fiend Volf Redux
Arm your True Dragon Sword and head for the center of the arena. Volf's Centaur Fiend companions will make your life very difficult if you are not careful. Take them out with either Flying Swallow attacks which can prove to be long or you can use fire ninpo if it's level 3 it takes them down with 1 use on 2 or 3 at a time and try to avoid Volf's area of effect attacks. Try to Flying Swallow him from behind and then lay a quick combo on him. Repeat. He will fall rather quickly. Watch the cutscene to end the chapter.