Speak to Mathias Shaw in Stormwind.
Find Shaw in Old Town. Let him know that the Lescovar threat has been dealt with and about your involvement in the Lord's plots against the city. I'm sure he'll be proud to have another hero among Stormwind's citizens.
He'll more than likely send you off to meet with the Prince or some other noble. Don't let it get to your head, <name>. The nobles can think they rule the city all they want, but some things remain out of their hands.
He is dead, then? Your justice was swift, <name>. I pray to the Light that I never become your quarry!
<He laughs and claps you on the shoulder.>
I mean no criticism, <name>. How could I, being the master of all assassins? But in truth, you have done the people of Stormwind a great service, and for that, I thank you.
Upon completion of this quest you will gain: