Well, if you think back to that fateful moment in Vampire Diaries Season 3, Episode 5 when Klaus killed Tyler (Michael Trevino) in order to create a successful hybrid, you’ll have your answer. For a werewolf to become a hybrid, they must drink vampire blood, die, and then drink the doppelganger’s blood.
Using the doppelganger’s blood was how the Original witch planned to ensure that Klaus wouldn’t be able to create hybrids. Elena was supposed to die in the sacrifice ritual that unlocked Klaus’s werewolf side. But when Elena came back to life after the sacrifice, she created endless hybrid opportunities for Klaus — until she became a vampire.
So now Klaus wants Elena to be human again so that her doppelganger blood can help him build a new family, because we all know that Klaus hates nothing more than loneliness.
Samantha Highfill is a contributing writer to Wetpaint Entertainment. Follow her on Twitter at@samhighfill.