"One, I hope, since if you met another one that would indicate I was dead. But if Slayerish senses in particular get something from you, it's likely that there's some other kind of magic somewhere that gets something from you too. And I wouldn't know what kind it might be or who might have it. Magic doesn't tend to come in perfectly unique kinds without any overlap in scope. There's only one Slayer, but there's other magic that improves your strength or reflexes or lets you sense things most people can't or gives you unreliable, uninformative, and unpleasant prophetic dreams. Can you tell which part of the Slayer package I like the least? I bet you can."