Who Is Keldor?
(I should've made this post six months ago when the CGI show first came out. But at that time everyone in the fandom had already been in the fandom for years and knew who Keldor was. This post is for all the new fans just tuning in.)
Keldor is a character that was first introduced into the Masters of the Universe franchise in 1986 in the "Search for Keldor" mini-comic.
Keldor is the brother of King Randor (Adam's father, making Keldor Adam's uncle), but he's been missing for years. Since before Adam was born.
However, while Keldor is mentioned by name and the conflict of the comic is Randor searching for his long-lost brother, Keldor, the character "Keldor" never appears on-panel. It is heavily implied in the issue that Skeletor is really Keldor and that is why he's so adamant about preventing Randor from finding Keldor; and this is later confirmed in an interview with the head writer of the comic. But it is never said outright in-universe that Keldor and Skeletor are the same person in the 80s run of the comics.
In the Mike Young Production reboot of MotU from 2002, Keldor and Skeletor are unambiguously the same person.
The very first episode of the series begins with a battle between Keldor and Randor in which Keldor's face is splashed with acid. It then cuts to 16+ years later and a shadowy figure dressed exactly like Keldor attacks our heroes. Randor calls him "Keldor" and the shadowy figure lowers his hood and declares his new name to be "Skeletor". In a later episode, Evil-Lyn has a flashback that shows the audience exactly how Keldor became Skeletor.
There is no mention in-universe of Keldor and Randor being brothers in this iteration of the franchise, and the two characters don't appear to behave or even banter like brothers. However, its possible that neither Keldor nor Randor know they're half-brothers, because the 2002 show bible for the series is very clear on the subject.
In DC Comic's 2012 run of the comics Keldor is a much more tragic character.
He imparts his backstory to a young Adam in the first issue of "Prelude to Eternity War".
Keldor never knew his mother, but the story his father told him was that she begged his father, King Miro, to take Keldor with him when he left her because she thought Keldor would have a better life with his father. But King Miro was ashamed of Keldor and never allowed him to find his mother or even visit her homeland.
(I have opinions about DC's versions of Keldor and Miro, but that's a subject for a different post.)
At the end of Eternity War (the conclusion of the DC run), its explained that Keldor originally sought the Power of Grayskull to prove his legitimacy, since his father always saw him as a mark of shame. But along the way, Keldor's quest for Daddy's Love was corrupted and became just another generic quest for power.
(Like I said, I have OPINIONS about how DC chose to handle the franchise. Not a lot of them are positive.)
"The Secret Origins of Skeletor" (2012) tells an abridged, but much more compelling version of Keldor's story.
At the same time that DC was butchering giving its own take on the franchise, Mattel was still publishing their own mini-comics to be included with the toys. The rare King He-Man action figure of the Classics line came with a mini-comic entitled "The Secret Origin of Skeletor".
Keldor and Randor are half-brothers, they grew up together, fought side-by-side in the Great Unrest, bled together, and mourned their father together. Keldor was the older brother and should have become King, but his step-mother (Randor's mother) suddenly and inexplicably died (off-panel) and Keldor was implicated in her murder. Instead of becoming King, Keldor is banished as a criminal.
He goes on a short quest to find himself -> finds Hordak instead and becomes his apprentice -> steals the Havoc Staff from his future father-in-law -> betrays Hordak -> forms his own group and returns to the capital to try and take back the crown that should have been his -> gets his face melted.
Like I said: its an abridged version of his story. Things happen quickly.
Finally, that brings us to-
Masters of the Universe Core/CGI (2021)
Why, fandom, don't you recognize your Uncle Keldor?
No, "Keldor", we don't! You're supposed to be fucking blue!
Okay, but, actually, bland color palette and boring and uninspired character design aside, this is actually probably really the most fun version of Keldor so far.
This post is being made specifically for new fans just joining us, so they're most likely already familiar with this version of Keldor.
At some point when Adam was six he staged a coup to take over the throne. During the coup he kidnapped Adam and absconded to Castle Grayskull with him, but Keldor failed to win the Power of Grayskull and got cursed instead. Ten years later he comes back, makes more bad decisions and becomes Skeletor. Then continues to make even more bad decisions and gets himself killed and becomes a ghost haunting Krass through the Ram Stone in her helmet.
(There's also a version of Keldor that never became Skeletor and became He-Man instead. From the 2019 comic “Masters of the Multiverse”.)
