"They teach you very basic moves, so you get these two big sticks like you're a 4-year-old boy and then, if you don't hurt anyone, they give you a plastic sword and you feel like you've passed a test," Headey told Access Hollywood.
"I made it to the plastic, and then I hit a couple of guys in the nuts," she continued laughing. "Yeah... and I went back to sticks. I was downgraded."
The second installment of 300 follows Greek general Themistokles as he "leads the charge against invading Persian forces led by mortal-turned-god Xerxes and Artemisia." Headey said she was surprised when she got the call for the sequel given that her on-screen husband in 300 Leonidas (Gerard Butler) and his men all died in the 2006 film.
"At first I thought they're mental, 'cause everyone's dead, so I don't know what they're going to do. Is it gonna be a rom-com? Um... I meet a new Spartan," the Games of Thrones star said.
"I found it interesting two fold, 'cause I thought it'd be cool to see Gorgo from a different point of view and see what happens to her when Leonidas dies, which you didn't see in the first movie. It just kind of brushes over that in terms of her point of view, and also I get to wield a sword, which I was quite happy about," she said.
300: Rise of an Empire hits theaters Friday.