They were question that Istas was not so sure would be safe to ask, now that she stood before Kuk in person. But to say nothing now would be to show weakness. That would be even riskier.

"You wish to eat this world, but you promise our own worlds will be spared, in return for our assistance. But a Hunger that demands to eat an entire world is a Hunger that could never be sated. I know this, for I am Waheela. We are creatures of ice and snow and cruelty, and our Hunger is unending. And yet, it is not so great as yours. What proof can you offer that your Hunger would never turn against us?"

Istas doubted that such proof could ever be provided. Except, perhaps, sparing this world...which was obviously not what Kuk wished to do.