After getting the fourth tablet and leviatan appears,simply go down the waterfall by goind around the room.
If you don't want to fight Neo Exdeath (the transform of Exdeath) you need to use the command Mix (an ability of Chemist Job), then mix the items Maiden's Kiss & Holy Water to create Kiss of Blessing, then give it to Exdeath and kill him, he won't transform to Neo Exdeath & you can see the ending.
Before venturing into the Cleft of Dimension, return to the Town of Mua. In the southwest, a door that was previously locked is now open. Through the door is a hidden path that will lead you to a man. He will offer to give you a Brave Sword or a Chicken Knife. The Brave Sword will get stronger as you win battles and the Chicken Knife as you run from battles.
In Kelb town, enter the Inn. You'll find a man sitting on a table talk to him then sit on the chair on the LEFT (NOT in front of the man)! He'll give you some kind of wine then he'll give you an after meal gift of 8 Potions! You can repeat this over and over to get more Potions!!