For Samuel, choosing between continuing or retreating wasn't an easy choice. He needed to consider more than just his own thoughts.
The injured adventurers reasoned for him to turn back but the sense of urgency in his heart couldn't be so easily suppressed. His fear of this hidden threat couldn't be so easily extinguished.
If they left who could guarantee that they wouldn't face another similar boss on the way back? This one respawned abnormally fast after all. They also might not have Eon to help them in a second attempt.
Well... maybe the quick respawn had something to do with the lich's sacrifice, so it could take longer next time. But Samuel couldn't verify that and as long as the possibility existed there was a risk involved with retreating.
It was at this time that Samuel remembered the words of Miller.
It was only a scouting mission.
The job was already done.
Retreat. Pushing forward would only lead to more casualties.