This quest is not available in game.
Get Astor's Letter of Introduction and return it to Mennet Carkad in the Rogues' Quarter.
If you wish to join the Deathstalkers, Lord Varimathras' elite guard, you will have to prove your worth.
I will not lie to you, <name>, this task could mean your death.
I have some things that need attending to. I require the personal effects of Astor Hadren, a messenger who travels between Silverpine and the Undercity. I will leave the method of procurement to your discretion.
It will be better for you if you know less of the nature of this business. Succeed and I shall tell you more.