The next body that you need to possess is the Armor. It can be found to the left of the entrance to dungeon 4. You should still be powered up enough to remove blue blocks, so you should have no problem clearing away the block that prevents you from reaching the ladder to the far left of your current room.
Climb up the ladder and head right to face the Armor. You can leap over to the far right side of him and attack him safely from a distance. He should go down in two hits. You will swap bodies. Now you are in control of a body with a very strong attack power, but your attack range has been significantly reduced, and you will have to adjust to getting very close to your enemies before attacking again. Despite the Armor's power, this can be difficult to get used to for a while.
Your next goal is the entrance to dungeon 5, which is actually found in the lower left corner of the fortress where you began the game in the first place. However, in order to achieve enough power to break down the blue blocks that surround the dungeon, you're going to need to collect 8 sword items first. In order to do this quickly and safely, it is a good idea to pretend that you are on your way to the first dungeon entrance. Here is where you can collect a number of swords.
2 are contained on the left side of the room where you defeated the Armor.
2 more are found in the room below, one in a statue (which you may have collected as the Sorcerer, and one hidden in the block to the right of the ladder that leads to the room below.
One the way to the first dungeon, one sword will be found in the statue above the first Blaster you encounter, and another sword will be hidden in the wall all the way to the right of the second Blaster you encounter. After you gather these two, start heading back to the starting point.
When you are one floor above the starting point, you will drop down to the left of an orange door. Use a key to open the door and collect a sword from the statue. Then when you are in the starting room, attack the wall to the right to collect energy and another sword before you drop down and face the Bouncer.
Once you have collect 8 swords, you will be capable of chipping away the blue blocks that surround the fifth dungeon entrance. Defeat the Bouncer and clear a path to the entrance.
Make no mistake, this dungeon can be challenging, but only if you attempt to rush through it. The third level down is dark, so you will need a few lamps to get through it. The trek to the dungeon boss is relatively easy as long as you stop to see how far enemies are allowed to travel before you advance and attack.
The first real challenge comes when you reach the bottom level. You will have to avoid getting hurt by a caterpillar and two flames before you reach a spot where you will have no choice but to take damage. A Skeleton roams a very small space below a statue that contains energy. There is absolutely no way to avoid getting hurt by it. Your best bet is to crawl below the low ceiling and continue straight into the Skeleton. You will get hurt, but as you fall to the ground below, you will automatically stand. As you stand, attack immediately, and you should be able to remove the Skeleton before it can do any more damage to you.
Once you clear the Skeleton, collect the energy above it, and from the statue beyond before you encounter the guardian. Like all other guardians, this one can only travel to a certain extent across the screen. As long as you stay on the ground before the rock that the boss floats above, you cannot be hurt. Simply jump in the air, and attack so as to hit the guardian on the top of its head. Three hits will be enough to defeat it. The head to the back to hit the statue and collect the YAROVI idol.
Heading back to the fortress won't be any more difficult than when you were traveling to the guardian. Just be cautious and get a feel for how far the enemies may travel. If you are slow and careful, you should be able to make it back to the fortress without taking any more damage.