What was the price to pay for the fusion skill of the Douluo Continent's God of Destruction and the Goddess of Life?

The cost of the fusion skill of the Douluo Continent's God of Destruction and the Goddess of Life was that the user had to endure tremendous pain and pay a heavy price. This kind of fusion skill would usually cause great damage to the user and might even cause the user to die. Tang Wulin, the user of the fusion skill between the God of Destruction and the Goddess of Life in the novel Douluo Continent, had once experienced tremendous pain and paid a terrible price when he was attacked by a powerful attack while using the fusion skill.