Kor'sarro Khan is what you would get if Genghis Khan rode a motorcycle. He is the captain of the White Scars' 3rd Company, and the Master of the Hunt for the White Scars. He wields a special relic blade called Moonfang and rides a bike called Moondrakken. Sammael wishes he was this cool naturally, and has since overcompensated by nixing the last Imperial Jetbike, rocking an AP2 Sword, Eternal Warrior, and a fucking plasma cannon... on second thought, Khan might need to step up his game just in case, though the man himself doesn't mind as much as one would think.
Since he is technically a Captain, he uses the "all Bike squads become Troops choices" special rule so long as he is on his bike Moondrakken. As Master of the Hunt he gets D3 extra victory point if he slays the enemy Warlord in a challenge. Other than that, he is basically a normal Captain with Furious Charge (which he does not confer to his unit), a Power Sword which also causes Instant Death on to-wound rolls of 6. and the ability to make D3 Hammer of Wrath attacks with Moondrakken. But, more importantly, as the Master of the Hunt, if he is the Warlord he gives every White Scars bike unit or unit embarked in a Rhino or Razorback the Scout special rule, which also allows them to outflank, consistently altering the way your Detachment work and transforming it into a fast and unpredictable army.
Kor'sarro, from the times he shows up in stories, is actually a pretty cool guy. Like your archetypal White Scar, he combines a carefree love for his job, a sharp and insightful mind, and killer instinct into one super-speedy package. When he worked with his bromantic partner Kayvaan Shrike to hunt Voldorius, he helped ease tensions between the chapters by citing a battle where the White Scars were the ones who left the Raven Guard hanging to make a point that they should move on from the past and focus on the present. He still prefers the White Scars' free and open style of war over the skulking of the Sneaky Beakies, but that was a pretty bro move considering how proud Space Marines tend to be about battle honours and past insults.
And when meeting Sammael in a joint operation, he tried to strike up a rapport with the stoic Dark Angel, privately reflecting that while he'd love to pilot a jetbike just to better resemble Jaghatai-senpai, he honestly preferred a conventional Space Marine bike because it got a lot more physical and close to the earth. He has also killed Doomrider - wait, what?
In other news, he may have a something-mance with Shadowsun. Read the Damocles collection, and all will become clear. She had the chance to melt his face into a sludge, but didn't, instead talking to him in his native tongue and offering him a drink. Conclusion? He likes her, she likes him, and stuff. He did end up stabbing her though.
With his DICK, bitches!
Upon getting his first look at the Primaris Space Marines Kor'sarro immediately demanded that he be made into one despite nobody at the time knowing if such a thing was even possible. The procedure was a success, but it appears to have gotten him into some hot water with Jubal Khan. It did get him the finest cyber-berkut the White Scars have, but since it records everything it sees some think that it may be a way for the Chapter Master to keep an eye on the Master of the Hunt.
On the Tabletop
Kor'sarro is a White Scars captain equivalent and a sober, loyalist version of Doomrider. His special rules are And They Shall Know No Fear and Chapter Tactics (White Scars), which gives all bikes/rhinos/razorbacks scout, Furious Charge, Independent Character, and Master of the Hunt (gives D3 victory points if he slays the enemy warlord in a challenge). His warlord trait "Champion of Humanity" allows Imperial units within 12" of him to reroll morale and pinning tests. Kor'sarro comes out of the tin with power armor, frag and krak grenades, an iron halo, a bolt pistol, and the relic blade Moonfang, a power sword that causes instant death on a to-wound roll of 6. He can be upgraded (25pts) to ride into battle on the relic bike Moondrakken, which is a Space Marine Bike that gives d3 hammer of wrath attacks instead of 1.
Kor'sarro is a great warlord for any White Scars army. He's fast, he's killy, and he's really cheap for what he does. Being the Master of the Hunt he's good at chasing down and murdering warlords, and his warlord trait means you don't have to worry about anyone faltering behind the advance, though this usually isn't much of a problem with marines.
As a Primaris, he doesn't have the bike but does gain the ability to deal mortal wounds in the shooting phase and benefits from an improved Moonfang. His aura is also enhanced to add a +1 to wound for all melee weapons, so put him in an Impulsor with some veteran Intercessors (don't forget the sarge's Thunder Hammer!) and you're set.