Everyone else gave Jacob mocking looks when they discovered he intended to take on the formidable task of destroying the formation single-handedly. They doubted his ability to handle it because even Jonah and his companions had failed to do so even though they had sacred martial arts relics.
There is no way that Jacob could possibly destroy the arcane array on his own. Even if he knows where the core is, the arcane array is too powerful for him to destroy single-handedly. Virgil whispered softly, "Mr. Sullen, you…"
He wanted to caution Jacob to be wary of attempting to disrupt the formation, as those who had previously attempted to do so had died from the backlash. The elderly man from earlier was a Greater Martial Arts Marquis but unfortunately ended up sustaining severe injuries.