Gravis had to spend another 300 years just sitting around and waiting for his clients to finish.
One of them died, but the other ones managed to survive. During the tempering, these people hated Gravis and wanted him to die, but after they survived, they were thankful. They even apologized for some of the things they had said.
Gravis simply shooed them away, and when the last person left, he closed shop.
The Secret Name Torture Chambers vanished.
After closing shop, Gravis threw one last glance at the place he had been for a bit less than a thousand years.
'Just a thousand years for over ten billion God Stones,' Gravis thought. 'That's really an insane amount of money. Sure enough, creating your own business is always the fastest way to become rich.'