The Vampire Diaries returned with a vengeance for its Season 5 premiere (“I Know What You Did Last Season”), but we still have some major questions before TVD returns next week with “True Lies.” And at the top of our list is: why does Silas need Katherine?

Once again, Katherine is on the run from the Big Bad, but unlike Klaus, who needed Katherine’s doppelganger blood to break Klaus’s werewolf bind, Silas seems to need Katherine’s blood for another purpose. Since Katherine is the only known vampire to have ever taken the cure, we think whatever was in that cure is linked to Silas’s sudden interest in her.

Silas is no fan of vampires, so perhaps now that Katherine has been cured her blood can cure other vampires. This means Katherine could be some sort of weapon of mass vampire destruction! However, this storyline sounds all too familiar. Remember when Esther wanted to rid the world of vampires?

So maybe Silas needs Katherine for another purpose. We know Silas wants to destroy the Other Side to be with his true love, so maybe Katherine — and her blood — can somehow help him in his mission?

There’s also the theory that Silas’s lover was the original Petrova doppelganger. Now, we know Tatia as the Original Petrova, but what if there was someone else before her? It wouldn’t be the first time The Vampire Diaries Powers That Be threw in loopholes (i.e. Klaus’s werewolf-hybrid baby and the Sun and Moon Curse.)

However, one of the more plausible explanations for what Silas would want with Katherine is her humanity. Like Elena before her, Katherine is the token human with Petrova blood in her system. (How do you like that for karma, Katherine?) This makes her desirable for all kinds of rituals. With a string of mysterious new faces in Mystic Falls, namely Nadia (Olga Fonda) and Tessa (Janina Gavankar), perhaps one of them is after Katherine’s blood to take down Silas. This would explain why Silas is so desperate to get to Katherine first.

What do you think, TVD fans? Why does Silas need Katherine? Sound off in the comments!

Catch the next episode of The Vampire Diaries on Thursday, October 10, 2013, at 8 p.m. ET on The CW, followed by the series premiere of Reign.

Crystal Bell is an editor at Wetpaint Entertainment and our resident fangirl for all things The Vampire Diaries. Follow her on Twitter and Google+!