Song of the Deep and Brute Cavern were already on bad terms. Even so, Sliv didn't wish to be the one who worsened the problem because this would give Emmagan's group a new reason to alienate him in the organization.
When that happened, even Flunza wouldn't be able to cover him up.
Attacking Angor only worked to solve his personal grudge but would leave him with a ton of troubles to deal with later.
Sliv had decided to give in. Yet he couldn't do it openly or his mighty figure of a wizard would be ruined.
Jebra, as a bystander, saw both Sliv's concern and Angor's intention to escape, made a quick decision and stepped up.
"Angor, so you don't have the Mystery item. Then how do you explain the Mystery energy I detected from this place earlier?"
Taking the chance, Sliv canceled his aura and moved away, pretending that he was allowing Angor to speak more properly.