Veil

Jungles of Khyber
After you finally reach her by the last room in the quest, she will say:
 * Veil: First, my failure in the Vault of Night... and then the Inevitable chases me out of Stormreach... and now you, a mere, have slain my minions with contemptuous ease.
 * Veil: Were it another time in my life, I would punish you. But I am not the vampire I once was—yes, I am a vampire, did you not know? That is why the Inevitable is after me. It seeks to destroy all who cheat death.
 * Veil: So, will you kill me now, or am I to wait for my death at the Inevitable's hands?
 * You: I'm not here to kill you. Your friend, Marek Malcanus, sent me to help you.
 * Veil: Friend? I did not think that my friends would send help... I had forgotten what a powerful resource the right friends could be. How foolish of me!
 * Veil: I can see now that it was a mistake for me to leave the Laughing Knives. Were they here now, the Inevitable would be but a paltry distraction.
 * Veil: Very well. If you defeat the Inevitable here, I shall return with you to Stormreach and rejoin the Laughing Knives.
 * Veil: This circle will protect me while you face the Inevitable. If you fail, it will not last long....

After you defeat the Marut, she will thank you:
 * Veil: It seems you have rewritten my destiny. Come, let us return to Stormreach.

The Vault of Night
Veil is found guarding the ??? entrance.