Shadow Captain (Chapter Master) Kayvaan Shrike (AKA Captain Beakie/Beakie McAwesome or any other variation of such) is the shadow captain and a major member of the Raven Guard. He is fucking badass and wears the lightning claws once owned by Corvus Corax himself. He also has a supremely epic Beakie helmet to round out his old-school style. He's a sentimental old sod; when the rest of the company pushes off to deliver righteous asskicking on other foul xenos, Kayvaan prefers to stay behind and spend his time rescuing pockets of surviving civilians and soldiers, or assist the local imperial forces in killing off any left-over resistance. This makes him a goddamn PSEUDO-HERETIC for valuing human life above killing the Emprah's enemies, but hey, that's life in the grimdark future of the 41st millennium for you. Judging by his interactions with Ko'sorro Khan, he's even willing to look past the Ravens' millenia-spannng rivalry with the White Scars.
Back in 4th Edition, he even had a rule to lead a unique custom unit called Shrike's Wing, which were Lightning Claw wielding Veteran Assault Marines that Shrike personally trained. Pity they aren't available anymore, though you can take Vanguards for the Shadow Captain and call them Shrike's Wing.
He's also fucking awesome because he's named after one of the most hardcore birds in existence, the shrike, who are known for impaling their prey on brambles instead of outright killing them.
As of the 7E Warzone Damocles campaign, it's revealed that the Raven Guard Chapter Master, Corvin Severax (Whose crowning achievement was...nothing, really), got blasted by Commander Shadowsun. As they regrouped, the remaining Captains began debating over who'd be next and Shrike decided to take the initiative. Only time will tell whether or not this will reflect on his statline or with a new model... but as of right now he's Chapter Master of the Sons of Corax.