Apparently, the trappers managed to catch one of the sacred animals - the Divine Stag.
Serene had seen the mutilated corpse of the stag in the cart. Hence, the reason for her rage. Furthermore, there were also indications that the poor female stag must have carried a fawn with her, but in reality the fawn was nowhere to be seen.
The elven soldiers had found the possible clue of another trapper group, but the problem was there were three sets of tracks leaving this place. Serene needs to know exactly which path the other trappers went - the one who took the fawn.
Therefore, just like Tristan guessed, they wanted him to use his [Blood Seal] skill to make the captured trappers divulge the information.
"I am sorry, captain. I don't understand. How do you expect me to help in this matter? Please elaborate." Tristan said with a faint smile.