Since he's still grappling with flashbacks (and thus, drinking heavily to prevent nightmares), Cao Pi takes a moment before deciding how to dish the bad news.

"What I learned," he says heavily, "is that we have no chance against a fully grown, hale one. Swords will not pierce it. Even getting close to it will result in death for everyone involved. Trapped, wounded, and smaller, it still simply killed by sucking the light from a lantern. The long-range weapons Dr. Solis spoke of would be our only chance, but we may still all die."

It is, quite frankly, a lot more hopeless than it seemed when they had less info to go on. Maybe in a week or two when he's processed everything and the nightmares wear off he'll be more clear-headed and less fatalistic, but...that look in his eyes says it all. They're pretty fucked.