Your goal here is to jump past the fire spouts and enter the shadow gate at Exit B. If you scoot far enough forward on each ledge, then you'll be out of the range of the fire spouts, and you'll be able to make your jumps unhindered. If you land in the water, you'll have to swim to the shadow gate at Exit C and try the jumps again.
You'll find yourself in a maze of islands in the shadow realm. If you arrive here from Exit B, then you'll need to take the eastern gate, then the eastern gate, then the southern gate, and then the southern gate to escape the area. If you arrive here from Exit C, then you'll need to take the eastern gate, then the eastern gate, and then the northern gate to escape.
Note: If you get lost, you can try mapping the islands yourself. The easiest way to do this is to record where the other islands are in relation to the one you're on, and to use that information to distinguish one island from another (since the islands themselves all look about the same).
Your objective here is to climb to the top of the tower and activate the rune glyph (#5). To do that, you'll have to find loose bricks, which when pushed will lower ledges, which will allow you to climb to the next higher level of the tower. While you're trying to do this, enemies will spawn below you, and a shadow demon will patrol the ledges above you, and they'll all fling spells your way.
We had all sorts of trouble getting our characters to climb up on the ledges. The idea is to have your character face the ledge, and then to jump. The character should then climb up, but sometimes this works and sometimes it doesn't. Since you'll be pelted with spells the entire time, climbing to the top of the tower can be frustrating.
Note: If you don't have any luck getting your character to climb up onto the ledges, try aiming for the outer corner of the ledges rather than the center. We've also heard that doing backflips instead of forward jumps can be effective.
There are also two level 8 chests in the tower. They're positioned so that you'll have to jump down from a higher level of the tower to get to them. We'd recommend that you activate the rune glyph and kill the shadow demon first (especially since killing the demon seems to slow down the spawn rate of random encounters), and then get to the chests afterwards.
To exit this part of the Shadow Ruins, you'll need to jump from the tower to the ledge where the shadow gate is (Exit D). If you're at the top of the tower, then the easiest way to get there is to jump to the ledge to the west, and then to jump counterclockwise until you've reached the ledge with the shadow gate. The shadow gate there will only start working after you've activated the rune glyph and killed the shadow demon.
1 - Loose Brick
Pushing the brick here will lower the ledge at #1a, allowing you to climb up.
2 - Loose Brick
Pushing the brick here will lower the ledge at #2a, allowing you to climb up.
3 - Loose Brick
Pushing the brick here will lower the ledge at #3a, allowing you to climb up.
4 - Loose Brick
Pushing the brick here will raise a ledge at #4a, allowing you to climb to the top of the tower.
5 - Rune Glyph
You should activate the rune (so it lights up) when you reach it.