Even if the evil spirit seemed to have genuinely surrendered and accepted his death, Aster didn't drop his guard, Camila didn't remove the spears that were restraining it, and he didn't let go of the skull of the giant undead, at the slightest sign of the evil spirit trying to play any trick, he will kill it on the spot.
The girls on the other hand started picking the loot of the previous battle, all those undead had yin accumulation crystals working as their cores, instead of dantians, so after they were destroyed, their cores became resources for others.