The Time Lord is back in another series of adventures aboard the TARDIS in "Doctor Who" season 9.

BBC recently released an extended trailer of the series showing Doctor Who (Peter Capaldi) fighting with various forces of evil with his latest companion, Clara Oswald (Jenna Coleman). Based on the teaser, the time-travelling alien and his human companion will be facing a lot of difficult challenges in the upcoming season. Some of them are new villains, while the others are returning enemies who all want to defeat the Time Lord. 

One of the next opponents of the duo is the group of fire-breathing creatures with a cat-like appearance. This portion of the trailer also shows "Game of Thrones" star Maisie Williams, who is set to join the latest season of "Doctor Who" as a guest character in two episodes. 

Still, the trailer does not reveal the role that Williams will play in the series, and when exactly she will appear alongside the Time Lord. But based on her extremely brief appearance in the video trailer, several speculations about her character have surfaced. 

According to rumors, there is a chance of seeing Williams as the younger version of the Doctor's long-time frenemy Missy, who is currently being portrayed by Michelle Gomez. These rumors are based on the hair and fashion choices of Williams' character, which look very similar to the current appearance of Missy. However, BBC is still mum about the validity of the said rumors. 

Meanwhile, a fiercer Clara is also shown in the teaser. She is featured holding a rocket launcher and pointing a long sword at Missy. This could prove that Clara is becoming as fearless as the Time Lord when facing their foes. But the Doctor remains brilliant and daring as ever, and he even makes sure that his opponent remembers who he is. 

"I'm the Doctor, and I save people! This is where your story ends," the Time Lord declares with a threat. 

"Doctor Who" season 9 is slated to premiere on Sept. 19 on BBC and BBC America.