They had the urge to kill vampires-even if that wasn't their purpose. What sort of creature were they trying to prevent? It couldn't have been a vampire if they were older than you, so why target vampires?
[He's trying to follow you here.]
In 'irrelevant' do you mean the spell just ended once their mission was completed. Or they failed in their mission?
[He doesn't mention them, but he does file those two tidbits away. Werewolf venom works on regular vampires such as Damon and Stephen and the stake from a tree that was used in their ritual works on more powerful such as Rebekah.]