When What We Do in the Shadows returns for Season 2, Guillermo will be back with a new skill set and a new attitude. During a set visit, the cast and crew of the FX series revealed the vampire familiar has a major role to play in the upcoming season. What's more, they teased how the mild-mannered character will evolve into a natural-born vampire killer.

"Obviously, a big part of this season is we ended last season on a big question with Guillermo, as to whether he's a vampire killer by DNA or whether he still can be a vampire," executive producer Paul Simms explained. "That's one of the biggest arcs we play out this season -- his struggle to figure out what he exactly is and how it affects his relationship with Nandor."

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"Since the vampires escaped the Council, and we never tied up that thread or referred to it. We do now, which is that in the time that has lapsed between last season and this season, the Vampire Council has been sending assassin after assassin to kill Nandor and Nadja and Laszlo, and Guillermo has thwarted them every time without Nandor or Nadja or Laszlo even noticing that he's working above and beyond and they still treat him like a slave, basically. And that's really funny," he added.

For Guillermo actor Harvey Guillen, that meant he had to step it up in the stunt department. "We're definitely gonna dive into the Van Helsing side of his background and it's in him. He's obviously killed vampires by accident in the first season, and in Season 2, we start off with killing more," he teased. "This year, I showed up and they were like, 'So there's gonna be a little bit of stunt stuff.' I was like, 'Oh cool! How fun!' It was like, 'Yeah, so here's your trainer, and you have boxing on Saturday.' And I was like, 'Wait, what's what's going on? What's going on?' And they were like, 'So this is happening,' and like day one, we're shooting the first episode. I'm killing a vampire going through the window, and it's like Buffy. Guillermo is the new Buffy the Vampire Slayer. It's like one, two, three -- backflip! I jumped out of a window last week."

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"Of course, Guillermo is tapping into his vampire killer genes -- his Van Helsing genes -- and that's giving us a lot of fun, a lot of opportunity," agreed stunt coordinator Tig Fong. "Harvey is actually a shockingly, surprisingly physical actor that his form might not belie, but he's actually incredibly coordinated and he's just gung ho. He's super excited about playing this character and about this new direction of his character. So, you know, we throw vampires at him that he kills, so it's a lot more action-y this year than it was last year for sure."

While vampire killing comes naturally to Guillermo, that doesn't mean he embraces his new skill set right away. "It's always been in him, but he's trying to fight it," Guillen insisted. "Also we find out that he's still loyal to the people that he loves, especially with the relationship that he has with Nandor and he's just still protecting them, even after -- I mean, these vampires are really sometimes awful to him, obviously with the way they treat him, but he's still a human being and we're all human and we all care about each other. We forget that he's the only human, so he actually does have feelings. He thinks twice about doing something. He wants to be loyal. So that part of him is still thriving."

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"He doesn't know how to manage it," he continued. "He's put in a scenario where he has to be quick and he does it and, after it's done, it's like, 'Oh my god!' It's done! So I kill a vampire in the first episode and it happened so quickly that literally he's on the floor and I look at the camera and I'm like, 'Oh my god, I'm sorry!' You know, so I apologize for being a good natural born killer. It's like, 'I'm sorry! I'm so good at killing vampires!' Yeah, he apologizes."

Nevertheless, Guillermo's new vampire hunting prowess will begin to change his attitude towards his vampire roommates, particularly Nadja and Laszlo. "You'll see more of him like snapping because he's coming into his own," Guillen said. "So he's like, 'I'm not answering to you.' To me, it's like, 'I'm not even your familiar.' There are moments where he talks back to Laszlo and Nadja, and even Laszlo is like, 'Ooh, saucy!' Even they're like, 'Guillermo is acting [out] a little,' and it's like, yeah, you can only push so much until you take too much shit and are like, 'I'm gonna blow up.' And also knowing that he's like, 'You know what? No, I'm not gonna take shit anymore,' so I really like that, this season, he's starting to question things more."

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"The vampires are so selfish that they don't realize stuff is going on," he elaborated. "Like, you know, I get home covered in blood, and they're like 'Where have you been?' No questions asked! In episode four, I come home completely drenched in blood and they're like, 'Nice! Is that tie-dye?' I'm covered in blood! [Matt Berry's Laszlo] is like, 'Did you go to a concert?' And I was like, 'Yeah, you know, Vampire Weekend.' And it's just like, 'Great, great.' No one even cares what he's doing! Sometimes, that's the joke -- like I'm in the middle of fighting and killing the assassin... I'm killing vampire assassins sent from the Council."

Of course, one of the reasons the vampires don't notice Guillermo's new deadly activities is because he is also keeping them a secret. Asked if he warns his master Nandor about the Vampires Council assassins, Guillen said, "No, because then he would have to admit that he's a vampire killer. There's so many levels going on this season! It's like 'I have to keep a secret. I have to protect them. They can't know that I'm protecting them.' There's a lot of pressure for Guillermo. No wonder he throws himself out of windows!"

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Although Guillermo still has his heart set on becoming a vampire, it looks like Nandor doesn't have any plans to carry through on that promise, at least in Season 2. "He's never going to make him a vampire! Because if he makes him a vampire, he's going to lose him," Nandor actor Kayvon Novak revealed. "He wants to keep him close. He wants to keep him needy. I believe that he has a real affection for Guillermo. You know, he does treat him badly sometimes and he does talk to him badly, but Guillermo always forgives him and I think sometimes Nandor can't help but be a bastard to him, but he still forgives him. I mean, he's kind of enabling this very bullying behavior, you know?"

"I always feel slightly nervous, playing Nandor and being mean to Guillermo because I worry that he can pay me back in the ultimate way by killing Nandor and therefore killing my career in the process. I'm always like, 'Oh, do I have to be that mean?' So we'll see!" he added.

Returning Wednesday, March 15 at 10 pm ET/PT on FX, What We Do In The Shadows stars Kayvan Novak, Natasia Demetriou, Matt Berry, Mark Proksch and Harvey Guillen. Taika Waititi co-produces alongside Jemaine Clement, Scott Rudin, Paul Simms and Garrett Basch.

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