Kardan Stronos is an Iron Father of the Iron Hands and the closest thing they have to a Chapter Master. His role is closer to that of the US President or UK Prime Minster than a normal Chapter Master. He was appointed by the council to act as leader of the chapter to fight the Farsight Enclaves. After the campaign, he resigned, returning control of the chapter back to the council, only to be immediately reappointed to face the looming threat of Hive Fleet Leviathan, pissing off a few other Iron Fathers.
What little we know of him is that he's about 90% machine, just like the rest of his Chapter. However, the remaining 10% seems to include most of his brain as he's smart enough to realize the point of a group ruling is that they don't all have the same ideals, which isn't something you get with all Iron Fathers. As such, he's been adding other ranking members into the Clan Council over the years, and been encouraging more healthy ways to deal with their emotions than just repressing them. This also worries a lot of the Iron Fathers, as Stronos doesn't have a very good track record in mastering his own emotions. During one campaign he was challenged by a World Eaters champion of Khorne to single combat. Although calculating that the simplest way to defeat him was by shooting him in the head, in the end, he charged the Champion while screaming at the top his lungs in a blind rage before decapitating him (which was stupid, the dishonorable do not deserve to be fought honorably - on the other hand, this will undeniably have morale boosting effects for his allies while also demoralizing the World Eaters because despite being insane, they are still subject to morale checks). May not be the most expedient method, but it gets shit done. He also has a massive boner for Razorbacks, believing firepower is the only major tenet of combat, and wants to outfit the entire Chapter with them. He is also "nice" by Iron Hands standards, meaning he will feel sorry for shooting civilians to get to the enemy or leaving allies to die because it isn't cost-effective to save them.
While his penchant for dealing with Khornates is effective, the enemy of the Imperium of Man that Stronos hates more than any other are the Necrons, viewing the soulless automatons as abominations in the eyes of the Omnissiah. Which also makes him a whole lot smarter than some Techpriests, who tend to start bowing down and worshiping the Necrons right as they're powering up the Gauss weapons. When expecting to face Necrons, he takes more forces than the Clan Council believes is necessary, not stopping until every Necron in sight is destroyed or teleported off the field.
He has an unofficial official crunch profile which reveals his full name: Kardan Smashfucker Stronos. He also has an official crunch "profile", in Clan Raukaan's Echoes of War missions, wherein he's represented by "any Chapter Master model you have, with the Axe of Medusa". Dropping Smashfucker's traditional Hammer/Claw for a Medusa/pistol (because the Axe is thankfully not Specialist), we get a build that's statistically weaker than a Thunder Hammer but 30 points cheaper than a Hammer/Claw, and still hits at AP2.