Craftly-san has said that we're not limited to go only to our own worlds... and that those who leave would keep their memories. If there is a way to do that, the people who escape would have the best opportunity to change things from the outside. They'd go home with their powers, and with their knowledge of this place and the rituals these creatures are perpetuating.

...changing things from he inside seems... next to impossible, if I may be blunt. Craftly-san in proof enough of that. Even his option was just a way to end a single ritual before there was too much bloodshed, as opposed to ending all of them.

Because those are the terms of his contract, and those will be the terms of the contract anyone who takes the deal will be bound to.

I think that we should leave behind someone who will want to help as many people as possible... but who doesn't have the power to make meaningful change from the outside. It wouldn't be as much of a loss.