Before battling Jade in Obelisk, he will ask you if you want to join him. Answer "Yes", and whenever he asks you if you want to change your mind, answer "No". Do not push any buttons and he will soon say, "I'm bored. Entertain me!". After this, there will be a battle scene. You will fight a D.Flea, a Crab, a Flower, a G.Slime, and finally an M.Slime which, when defeated, will give you 9999 experience and 9999 gold.