Who Is Rayner In Star Trek: Discovery Season 5? Kelleruns Explained

A new face has joined the ensemble for the final season of "Star Trek: Discovery," along with a seemingly familiar set of pointy ears. A character named Captain Rayner (Callum Keith Rennie) is poised to board "Star Trek: Discovery" for the show's last voyage on Paramount+, and at first blush, this new player appears to be a Vulcan or similar alien species. A TrekMovie interview with series co-showrunner Michelle Paradise, however, has revealed that Rayner isn't Vulcan or Romulan after all: he's actually part of a lesser-known "Star Trek" species called the Kelleruns.

"He's a Kellerun," Paradise told the outlet after also reportedly confirming the character's background to SFX Magazine. "We were looking for a species that not a lot had been done with them. We definitely wanted another non-human on the ship and taking care of things." Currently, Doug Jones' Kelpien executive officer Saru is the most obviously alien member of the Discovery crew, but the majority of the team is perhaps unrealistically human. This brief yet seemingly benign character description is itself a surprise, as the "Discovery" season 5 trailer sort of makes Captain Rayner look like a potential villain. He's initially seen screaming with fury right after a voiceover notes that the item the Discovery crew is after this season "could be very dangerous in the wrong hands."

While we may not know too much about Rayner himself yet, the Kelleruns themselves aren't an entirely new species. They've appeared in just one "Star Trek" episode ever, the season 2 "Deep Space Nine" outing "Armageddon Games." Like most societies portrayed in "Star Trek," the Kelleruns were neither straightforwardly heroic nor totally villainous. They survived a centuries-long war against a rival alien group called the T'Lani, and once peace was accomplished, both sides wisely decided to dispose of the deadly bio-weapons (gene-disrupting viruses called Harvesters) they'd created during the conflict.

However, their attempt to protect future generations from a dangerous weapon crossed into dangerous territory itself: the Kelleruns tried to assassinate Bashir (Alexander Siddig), O'Brien (Colm Meaney), and other scientists with knowledge of their bio-weapons in order to completely eliminate the threat of future war. By the end of the episode, it's clear that the T'Lani were also in on the assassination attempt, and the story ended with a lack of closure for both groups as the scientists in their crosshairs ultimately escaped.

If the Kellerun seems like a random species to bring back into the "Star Trek" fold, that might be by design. "Kellerun is one that had not been explored a whole lot," Paradise explained. "So we were able to also build some backstory for him and for his planet that we'll come to learn more about later." Since "Trek" canon only includes a brief window into the Kelleruns' history, with very little cultural detail or context, the race functions as a sort of blank slate that the "Discovery" writers can use to tell whatever story they want.

As for whether or not Captain Rayner is a baddie, Paradise told ScreenRant that he's on the right side of history this time. "I don't want to say too much about [Captain Rayner] except that he is a bit of an antagonist with Burnham [but] not in the bad guy sense at all," Paradise informed the outlet. "He's a good guy character."

We'll learn more about Reyner and the Kelleruns when "Star Trek: Discovery" returns for its final season on Paramount+ on April 4, 2024.