It has been said that the production for "Alien" started last March 29, 2020, and finished last April 19, 2021. The movie will start its story during the Goryeo Dynasty, and a time gate that connects the past and the present appears. An ancient tribe from the Goryeo Dynasty, Taoist, will meet the people from the present while in search of the legendary sword. After the movie was publicized a year ago, "Alien" made lots of headlines on the online community. Plus, what makes it more prominent is because of director Choi Dong Hoon. The said film is Choi Dong Hoon's comeback project and its preeminent cast lineup since the pre-production stage.