Costar Kathy Bates said her scene with Gaga "scared the s--- out of me"
Credit: Michael Avedon/Entertainment Weekly

Lady Gaga is taking her nickname – Mother Monster – to a whole new level.

Making her debut as a leading lady in this fall’s American Horror Story: Hotel, the singer plays the Countess, a murderous (not to mention, blood-drinking) hospitality honcho at the fictional and historically creepy Hotel Cortez in L.A.

In Entertainment Weekly‘s new cover story (on newsstands Friday), co-creator Ryan Murphy says Gaga, 29, was eager to get in on the gory action.

“She showed up, and she was wearing diamond pasties, a Band-Aid on her boo-ha, heels and a black veil that Alexander McQueen made for her on the day before his death,” Murphy tells EW (PEOPLE’s sister publication) of the crossover star. “Then the crew gasped in delight, and we were off!”

In Hotel – the fifth season of FX’s award-winning anthology – Gaga stars alongside a slew of series guests and mainstays. Matt Bomer plays Donovan, the Countess’s lover; Finn Wittrock is a hyper-sexual model who piques the Countess’ interest; Kathy Bates plays Donovan’s mother and a front-desk clerk; and Sarah Paulson returns to play addict Hypodermic Sally.

For Gaga – who’s engaged to Chicago Fire star Taylor Kinney – joining the cast was a dream come true.

“I always wanted to be an actress,” she tells EW. “I was terrible at auditioning. I would clam up. I was very awkward. I wasn’t particularly pretty in high school. I was sort of blooming. Now I’m here.”

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As for the star’s acting? One costar promises a chilling performance.

“We’ve shot one scene together. She walked past me and literally had one line, and it just scared the s— out of me,” Bates tells EW. “She’s really throwing herself in this.”

For more on Gaga, pick up the latest issue of Entertainment Weekly, on newsstands now