She didn't want to fail and let her species disappear from existence. As for Rina, she didn't think like Luke… he believed that no matter what happens, as long as you do your best, everything will be fine in one way or the other.
When night came, Luke clicked his tongue in annoyance, the pace he was receiving coins and experience from his skeletons decreased, so he couldn't see himself getting enough coins in time like that. He had to go out and hunt the frozen mammoths.
"I sure hope that something at least of the level of necromancy is in the tier 10 skill books list…" Luke thought while he was heading to hunt the mammoths.