Make it back to where the vampire was. Go past where he was, and go through the door and up. Use the earth rod on this plate and go down. Floor 4 is a really hard maze, I'll give you instructions:
Left, up, left, down, left and up, left, up, up, left, down, down, up, up.
Like always, there's a lot of chests if you wish to explore: (staff, 3400 Gil, 1520 Gil, 5450 Gil, 1455 Gil, Tent, Mythril Shield, 1250 Gil)
Come back and get the treasure chests after you beat Lich. You need hold on to all the HP you can. Now you'll be on floor 5. Just go straight up and when you can't go up any more, go to the left and down. When you go through the door, you'll see the earth crystal! But, you got a fight first:
Recommended Level: 12
HP: 800
Difficulty: 3/5
EXP: 2200
Gil: 3000
New boss music > joo. Anyway, Lich has some nasty attacks in store for you. His bolt/ice2 stuff deals out the pain. He'll cast sleep and slow on your characters. If he's feeling like he wants to play dirty, he'll just regular attack one of your mages/weaker characters and smear them in a hit. Start off the battle by holding no bars. Use fire3 if you have it, fire 2 works well too. Dia2/3 will bring the pain to him, keep attackers attacking. After while he should go down. Might take awhile since his defence is so goddamn high. If he manages to kill one of your characters (likely) just restart from the memo save you saved in front of him.
Now, get your group and go to the other side of the world to: