I bumped the Carcharodons up in the order of articles for a few reasons. First, RoockieBoy has been exceptionally patient and enthusiastic to see them discussed. Second, the only Chapter covered before them in the Forgeworld .pdf is the Red Scorpions, and they get enough attention already.
The Carcharodons Astra (or Space Sharks to long time gamers) are a sinister and brutal Chapter that prowls the voids outside of the Imperium, eradicating threats before humanity is even aware of them. As Reavers of the Outer Darkness, all Carcharodons cause Fear and any Tactical squad may exchange their bolter for a close combat weapon for free or get one in addition to their bolter for one point. Due to Blood Hunger, all Carcharodons gain Rage if after they destroy an enemy infantry unit in assault or force them to Fall Back. However, they have to consolidate toward the closest enemy squad they can hurt after the assault. This could leave them in poor position sometimes, but is a small price to pay for the associated benefits.
Combined, these traits allow you to make a dedicated close-combat Space Marine army at least on par with the Black Templar. In fact, the ability to have a close combat weapon, a pistol, and a bolter makes them even more flexible than Crusader squads. In addition, their abilities benefit the whole army rather than just the characters. While Black Templar are more likely to catch the enemy after breaking them, the Carcharodons are way more likely to break the enemy in the first place.
Of course, this has to have a downside, and it’s that everyone is terrified of fighting alongside the Carcharodons. They can only ally with Imperial armies, which are all Desperate Allies. This will hurt you if you really want to take allies, but won’t affect you at all if, like me, you have a illogical dislike of taking allies.
Tyberos the Red Wake
Tyberos the Red Wake is the Captain of the Nicor and Commander of the Carcharodons during the Badab War. Despite his unknown rank, he has a Chapter Master’s staline and rules (though he lacks an Iron Halo). He wears terminator armor, has a teleport homer, and carries Hunger and Slake, which count as a lightning claw and a chainfist. He can freely divide his attacks between the two in any assault.
Despite being an obvious combat character, Tyberos actually has some army-wide buffs. When he gains Rage, he and all other models in the army with Rage gain +1S for the rest of the battle. For an assault army, this is massive. It’s like Furious Charge that never goes away. Tyberos’ army can take a single Assault Terminator squad armed entirely with lightning claws as a Troops choice. While not the preferred armament for Terminators, they’re still a good choice, made great by being Troops. Finally, Tyberos has the exceptionally useful Warlord Trait, Savagery Beyond Reason. He, along with any unit he joins, have the Preferred Enemy (Infantry) rule.
Tyberos is a strong close-combat character, provides some useful buffs for a close-combat Marine army, and is a reasonable points cost to boot. Honestly, the only downside I can see is that he only has a 5+ invulnerable save. All in all, he really synergizes with the Carcharodons Chapter Tactics, and you could make a fun and reasonably strong assault Space Marine army. At least as strong as dedicated assault armies can be in 6th Edition.