As we could have predicted from the Unrelenting Hunt dataslate on Tuesday, the Crimson Slaughter Dataslate, Kranon's Helguard, features the contents of the Dark Vengeance box on the Chaos side along with the expansion bundle box that was released recently.
The formation is specifically a Chaos Lord, a unit of Chosen, a unit of Terminators, a unit of Raptors, a Land Raider, a Helbrute, and two units of Chaos Cultists. For taking this formation, the units gain the Fear and Stubborn Special Rules. Additionally they have a rule, Swarm of Phantasms, which forces enemy units within 12" of a unit to suffer -1 to their leadership. If two or more units from the formation are within 12", the enemy unit also suffers -1 to their Ballistic Skill.
The Swarm of Phantasms is pretty cool and makes all units in the formation intimidating. Stubborn is arguably amazing for Chaos Space Marines, as one of the often maligned issues is losing a combat by 1 and being run down.
One note is that units are chosen from the "Chaos Space Marines Faction," which to me indicates they will not inherently get any of the Crimson Slaughter supplement special rules.
Also today was a fluff story that joins the Shield of Baal story arc and introduces Eldar of the Iyanden Craftworld to the fight. It is only just over nine pages long, so don't expect too much. The story could be interesting though in that it could play on the recent WD teaser leak of an Unexpected Ally following the Blood Angels release.