Go to versus (on 2 players) and select kobra. Then go to the kuaton palace. When your opponent is by the edge do kobras grapple (R1) and if you kick him directly into the lava he will be able to walk on it!

To get him you go to Edenia and go to the center near the bottom and you will see Rain talk to him and he will say he is looking for a cave. Then go down to either like the bottom left or right corner and there will be a tent with Jade in it talk to Jade and she will tell you to go back and talk to Rain go back talk to him and go back to the tent and you will find Rain dead. Then go behind the tent and meditate untill it is Friday at 12:00 A.M you will see a box inside is the key to tomb OT enjoy Liu Kang.