Been fiddling with an alt-heresy. New primarchs.
Bil Goode - Cowboy. Traitor during the heresy, but just made his own government without turning to Chaos (referred to as a breakaway) with his astartes acting like sherriffs.
Tomas Macabee - Blank. Legion of blanks. In the weirdest situation for Astartes because they’re literally made as the cheaper mass produced version of the Sisters Of Silence. Loyal. Lost in the webway along with a cadre of Sisters.
Mahg - Big on discipline and training. Constantly feuding with the Emperor during the Crusade Loyal at the start of the heresy but disappeared after having an argument with the Emperor. Possibly dead, possibly washed his hands of the whole situation.
Belisarius - Likes using overly intricate strategies and plans. Considers himself the greatest strategist the galaxy has ever known. Surprising no one, traitor and sided with Tzeentch. Still alive, and has his magic daddy on speed-dial to become a Daemon Primarch if he’s about to get his shit pushed in.
Li Shoumin - Xianxia primarch. Breakaway traitor. Views genetic manipulation as the destiny of humanity and likes to fiddle with geneseed. Has managed to extend augmentation start for Astartes as far as 30 years as well as made female Astartes available but with a high rejection rate; its still in the works. Primarily uses Astartes to gather exception minds rather than create elite warriors.
Alaric - Imagine if someone stapled Konrad Curze to Angron. That’s basically it. Died ten years before the heresy at the hands of his brother Duranil.
Seshethkunaaz - Haven’t worked out the details, but in terms of personality imagine if a primarch was raised by Necrons. Traitor during the heresy but hasn’t sided with anyone; just sends his legion out to murder people whenever he can. Current status unknown, probably murdering people.
Duranil - Seer. Had visions of the Empire and decided fuck that. Evacuated as much of his homeplanet as he could, left to the eastern fringe of the galaxy. Spent most of the great crusade saving people that got on the wrong side of the Imperium. Killed Alaric while he was having his Legion ravage a world. Has strong control over his visions and uses them in combat for what is basically spidey sense mixed with the Force.
Michael - Basically Sanguinius. The greatest warrior amongst the Primarchs. Loyal in the heresy, died in an ambush in space from the Chaos traitors.
Nikola - Mechanicum Primarch. Loyal during the heresy, lives. Currently serving as Fabricator General of Mars. Very few augments since they don’t have anything better than “being a Primarch”.
Khaldun - Administrator type. Died during the War Of The Beast.
Rugarn - Space pirate. Refused to join the Imperium, later allied with Duranil after the War Of The Beast to form the Astral Coalition agreeing to focus more on the trading rather than the raiding.
Marceau - Not sure what I’m doing with this guy, but by the name I’m guessing I’m going to make him a mime. Nurglite. Daemon Primarch, forced to ascend after losing to Duranil.
Stygia - Vampire. Started out as a ritualistic practice on his home, as a way of showing respect to enemies during the great crusade, and after becoming a Champion of Slaanesh as a way of gaining power by eating souls. Loyal during the Heresy, switched to Chaos after the War Of The Beast.
Valin - Grew up on apocalyptic hive world post societal collapse. Think urban Mad Max. Very survival of the fittest; would force his legion to fight over wargear. Joined Khorne during the Heresy.
Sophereon - The arch-traitor. Not especially loved by his brothers, but universally respected for his understanding of philosophy (or, more specifically, the philosopher of their legions; he could easily communicate with any other primarch or member of a different legion on their own terms). Unlike Horus joined up with chaos as an informed decision; he knew what he was getting into and decided to do it anyway. Lost the heresy, launched mini black crusades every once in a while to hurt the Imperium. Gathered strength till in M36 he came back and managed to finally kill the Emperor. Forced to ascend during his retreat when Nikola, Duranil, Rugarn, and Nemo ambushed him after. Emperor ascended and now every Imperial Shrine world shines like a mini-astronomicon and Sophereon ironically made everything better for the Imperium.
Heilung - Raised on feral world, refused to abandon traditional belief system. Emperor agreed as long as he didn’t spread it or practice it openly, he agreed. Abandoned the Imperium after the heresy, has occasionally shown up when something really bad is happening.
Ford - Raised by space capitalists. Was disappointed by the lack of capitalism in the Imperium. During the heresy founded a breakaway realm. Has the highest standard of living in the galaxy for any government with over ~1000 inhabited worlds.
Gerald - Genuinely don’t know what I’m gonna do with this guy. Probably gonna keep him blank until I remember something specific I need.
Nemo - Alpharius with less of the memey stuff. Traitor but no one really knows where his loyalties lie. Has been observed as friendly with the Harlequins so possibly Chegorach. Also known to be friendly to the Orks so possibly Gork & Mork. All that’s really certain is that he absolutely hates chaos and the necrons. And probably also Seshethkunaaz but no one can tell if that’s just the two of them being weird or if its something specific.