"We still need to untether from the train first before we can do any of that." All of this is planning for the future when hopefully they have figured that part out, so Thanatos can leave the people here easier. One less reason why he should be selfish and stay to be whoever he wants instead of Death Incarnate.

Thanatos then falls silent. He's asking a favor of Idia, two in a sense, and he's honestly not sure how big of a task that is to undertake. It doesn't feel right not to give him something in return as payment. What can he do.... He'll try to think of something when he's on the train next. "When Mort is done with his food, I will return the dish, so please don't worry about it."