Personal lies.
Lies others told and affirmed.
A replica of the past.
Rex used these mixtures of factors to greatly amplify the Executor's blind optimism.
In the entirety of his manipulation plan in order to get what he wants, Gistella was the crucial piece—the heart of everything that he was planning. He was reluctant to send Gistella to the tiger's den directly.
He was afraid that something might go wrong and Gistella would be the sacrifice.
But there was simply no other choice.
Just like what the Witch said, she has the tools necessary to infiltrate the Executor's forces.
Since she possessed cursed energy, from the cursed creature incident that attacked the city, there was a lingering cursed energy inside of her, that would allow her to deploy the Damned Specter skill that Rex possessed in order to search for the Supremacy of One gem.