The trailer for 'Avengers: Doomsday' teases the return of new and old MCU stars — here's everything we know

Joe and Anthony Russo are returning to direct the next "Avengers" film, while Robert Downey Jr. will play the main villain. Jesse Grant / Getty Images for Disney Marvel's next film, "Avengers: Doomsday," is set for release in theaters on December 18. OG Avengers like Robert Downey Jr., Chris Hemsworth, and Chris Evans will return to the MCU. The movie also unites characters from "Thunderbolts*," "The Fantastic Four," and the X-Men series. "Avengers: Doomsday" finally has an official trailer,…