You give Agent of the Arcanum Sezzherei Slayer Token.
Agent of the Arcanum tells you, "There are few beasts on Dereth as feared and hated as the Margul Sezzherei. To meet one who has personally slain the creature... I cannot believe it!"
Agent of the Arcanum tells you, "You should be commended for your efforts. From this point forward, let it be known to all that you are the Sezzherei Slayer!"