Itachi's fears were realized as Fuugaku headed to the back of the trailing grounds, stopping by a small hill.

"How could you?" Itachi's voice cracked.

There was a hatch on the side of the hill, Itachi knew it lead to an underground room. He had never been through the hatch himself, but he had heard what the room was used for.

The Uchiha used it as a final attempt to activate the Sharingan.

A voluntary practice for those who wished to a "revelation" worthy of activating the Sharingan they may or may not posess.

It was a sensory deprivation chamber.