Using the Door of Truth is definitely out of the question, as it can't guarantee that this guy doesn't have some kind of thought-capturing ability. It could easily lead to information leakage.
Taboo Sun? Beast?
Neither of these seem suitable to bring out. It's not that Gary Smith is timid, but he's worried that the Exotic Entity won't be able to withstand the abnormality. He wouldn't want to end up losing his valuable Unconventional Items.
Finally, Gary Smith thought of an appropriate secret.
The creator of the Netherworld, the origin of the Seven Great Royal Trees, the information about the Death God Tree!
It doesn't involve himself and it's a huge secret.
If that's still not enough, he could also add the information that the evolution of the Dead Eye Tyrant is a layout by the Matriarch.
So he thought back in his mind...
Rumble!
The entire sea of clouds began to tremble, like an earthquake. Before anyone could react, they saw a terrifying scene.