What would be something unexpected for Cain and everyone in the universe but would be something different to us too?
I guess a Chaos tournament would be one...
"Hey, Slawkenberg, Chaos Gods here, we do like the idea of a Liberator figure, an unaugmented human that rises above other mortals and accomplishes great deeds, unknown to you, other five planets have had rising leaders whose armies have created incredible tech and soldiers who have done harm against the Imperium with their forces of Chaos, each having our favor and help, and thus we decided to do a tournament between all six liberators and a team of 5 they each pick to help them in a contest of strength and tech, the winner will be the official liberator and planet for the forces of Chaos moving forwards.
We will present Cain towards the other planets, but Cain, here are your future foes:
Ricky Big Log, this one is a particular favorite of Khorne, with his blessing and armor he got particularly strong being able to toss Leman Russes like nothing and beating Ork Warbosses in arm wrestling contests, the Liberator Of Brute Strength, this hulking gladiator took over his planet with brutal tactics and sheer quality of his men and war prowess, his side's tech overall leads to his men being superhuman as much as possible, being able to survive various attacks without armor.
Masked Soldier, a favorite of Tzeetch and Khorne, a man who refuses to say his origins and uses a camo mask, much like Ricky, he took over his planet, but with less soldiers, albeit his are also of extreme quality and above the average cultist soldier, a man with amazing tactics that can be a brutal efficient warrior much like his men, his side's tech generally favor poisons or anything that can disrupt other's tech and mobility.
Michael Balrog, heavyweight boxing champion of his world, tired of the nobility and wanting a better world, took over it with his fans, a favorite of Slaneesh due to embracing his desires, still a calculating tactician, do not underestimate him for embracing his vices, for when Space Marines invaded his planet, he personally defeated their leader and some of their best with his boxing skills alone...and his power armor, the uppercut that defeated the Space Marine leader is still the most watched video on his planet, his tech's side generally favors speed and mobility, with new military vehicles that are shockingly fast and can hit hard enough.
Andros "Butterfly" Leibniz, another Slaneesh favorite, born an orphan with nothing, this man became a master thief with amazing natural acrobatic and contortionist skills, appaled by the greed and ruthlessness of his world's leaders, he formed a guerilla army that took over with less casualities than anyone would expect, the man gets what he wants when he wants it, called a butterfly for his amazing speed and natural agility when he fights even without his armor or anything supporting him, much like their leader, their tech embraces and helps with stealth and stealing their foe's arsenal or secrets.
Todd "Phoenix" Laurentius- A favorite of Tzeentch, born a simple farmer in a world where the Chaos revolt was failing spectacularly, he was a genius ignored by his birth and nepotism who joined the side of Chaos even when it seemed about to die, starting with a weak team of six, with his sheer tactical prowess and plans, he gradually led the team and then the side of Chaos to success after success, no one being able to predict and stop his plans, when the Eldar tried to attack and got repelled, a captive Eldar could only describe his mind as being like that of a Dark Eldar Jester if not superior and commited suicide out of sheer terror, a man whose plans have never failed against the Imperium or Xenos he faced, a man who is actively involved in creating new technology, his tech doesn't...specialize in anything as much as it all generally improves their vehicles and arsenal as much as possible, not exactly the strongest or fastest liberator, but one whose planet is well run and at the verge of starting conquering other planets as Todd created a space fleet out of almost nothing."
Cain, these are the men you will have to beat in a tournament to decide who the true liberator will be, as for why we are doing this...even we get bored, Khorne wants to see promising soldiers fight to the death, Slaneesh loves the idea of a big spectacle and Tzeentch wants to see what kind of plans and technology each side will bring...Nurgle is on a metaphorical corner of the Warp crying about lack of attention for some reason."
Let's face it...Cain would probably manage to beat all of them without killing any of them, they would be so overwhelmed with gratitude, respect and adoration that they would all join under him, and Cain gets amazing tech, amazing men and 5 more planets under him much to his ever increasing panic and disbelief.