In “The City on the Edge of Forever,” the Guardian of Forever told Captain Kirk that it “couldn’t change,” but nine centuries later, we return to find that the Guardian of Forever has changed, and now lives in disguise as a kind spacetime entity named “Carl.” In the Star Trek: Discovery Season 3 episode “Terra Firma Part 2,” we learn that the portal Georgiou stepped through in Part 1 was no ordinary door. Yes, it took her to the Mirror Universe, but now, it seems, it will take her to another time — back before the Prime Universes and the Mirror Universes diverged.

The powers of the Guardian of Forever have returned, for the first time on screen in four decades. First introduced in the famous Original Series episode “City on the Edge of Forever,” the Guardian of Forever has only been glimpsed one other time before this week, in The Animated Series episode “Yesteryear.” Still, despite these scant appearances, the Guardian of Forever remains one of Star Trek’s most enduring images. Now that it has returned, it's time to set through our own time portal and briefly explore the various secret histories of this gateway to the past.

As a result of spacetime anomalies, parallel dimensions, and temporal inclusions, the history of the Guardian might be confusing. To help clear things up, here are seven things you (probably) didn’t know about the Guardian of Forever. Behold!

Star Trek: Discovery streams exclusively on CBS All Access in the United States, airs on Bell Media’s CTV Sci-Fi Channel and streams on Crave in Canada, and on Netflix in 190 countries.