Magnus is a complicated fella. We still don't fully understand specifically the relation between him and the Leaper Demon King who becomes Mehrunes Dagon (as seen in the Seven Fights of the Aldudagga). The Leaper's role in that myth is strongly indicative that a correlation exists. It's possible he is a "mirror-brother" of Magnus, in the same sense that Akatosh and Alduin are the same and yet different. If we're lucky we'll find out more in Skyrim.
I also am strongly prompted to quote an interesting Nibenean story concerning the Leaper and Magnus' relation posted by one "King Bendu Olo" a few months ago. Whether they were a dev, librarian, Maruhkati or lunatic I am not wholly sure, but it stuck with me and I found it interesting and you may take it as you will:
When I was but a lad, my great-granddaddy (honest-ish Nibenese he spoke, dead langauge now, 'membered only by ghosts of the past such as I) told me a story of a naughty demon who would leap places Aka' said he couldn't. He leap'd so many times he tore a big [censored] hole in the sky (and he made sweet love to that gaping hole, making children uncountable, some of them naughty like he, like that young girl of his, Meri-something-or-Raga-Dia), so big that the even bigger dragon (he's bigger than big, he's like huge) actually noticed that damn hole, so he asked the demon "Why you leaping so hard little devil?"
The Devil replied "Piss off!", so Aka' sequezed that demon hard between his tail (making him six feet shorter), "Okay! Okay! I leap because I visioned true end, destruction, destruction of everything! Horrible! I must escape!".
So anyway, Aka' then punched that Devil so hard he sent him to hell, and made him a grand 'ole prince, even though some say that some missing man or greedy god tricked that demon blind (as he does in all stories, that wiley & slippery fish).
That's granddaddy's story (of a story of myth of legend) as I 'member it anyhow.
...Oh, the point of the story is that the Devil-who-is-Magnus-who-is-Akatosh-hu-is-Dagon isn't who he used t'be (you get like that after being so many other people), and instead of run'n he is now fighting (well Aka' did corner him), which he is doing so he can stop playing Akatosh and be true freedom again (because a 'red' freedom is just revolution) and run away. Ofcourse the only reason why he's Aka' is because he saw himself as Destruction, which caused him to see the BIG God, which meant... [NUMMIT]