Ryan Murphy, the show's co-creator, showrunner and director, told journalists Friday that her character's name is Elizabeth and "she owns the hotel and she is sort of a very wealthy social doyenne who is consumed with art and fashion and people."
"She has a nefarious plan that is revealed in the first episode that plays out of the course of the season," he said. Gaga starts shooting Monday.
They've built the set "from the ground up" on the Fox lot with a working elevator, and cast member Kathy Bates calls the creation "jaw-dropping."
"Not just the hotel itself but the rooms...how they're decorated. You won't believe it," she said.
The season boasts a cast including Matt Bomer, Chloe Sevigny, Cheyenne Jackson, West Bentley and Sarah Paulson.
Viewers will also see some big former "American Horror Story" actors make appearances. "You will see people from various seasons check into the hotel," said Murphy.
He also teased that "AHS: Hotel" will be a lot like Season One in tone with psychological, primal fear being at the forefront.
For Murphy, who has two other shows in production ("American Crime Story" for FX and "Scream Queens" on Fox) said making "American Horror Story" is "one of the great joys of my life."
"It's exhausting at the end of a season but I'm so energized by it every year because it does reboot and the actors and the stars are so cool and I have a real passion for that," he said.
He also stays passionate by casting a troupe of actors like Bomer and Paulson, who he regards as friends.
"I've directed all of these actors in different incarnations and from it comes this great shorthand and I think they know that they are safe because we've worked together. They've seen other things that we've done, they feel protected," he said.
"American Horror Story: Hotel" premieres Oct. 7 on FX.