The general consensus of the intertubes seems to be pretty negative concerning the mandatory inclusion of a unit of Possessed Chaos Space Marines in a Slaughtercult formation of Blood Host detachment. I do not share these sentiments and here is why.
Yes, they are expensive, yes, they cannot shoot, but I have a hard time seeing these factors as making them so unattractive. With both Daemon of Khorne and mark of Khorne I think the buff these guys provide is worth it. Yes, they pay for these marks but never before had Demon of Khorne been available. Previously if the unit wanted furious charge they would have to purchase a 15 point icon of wrath. Factoring it all together these guys get furious charge for 10 points cheaper that the Chaos Space Marines codex albeit with the lack of the icon assault result benefits. They are fearless so don't need it anyways.
What's more, the icon in the Korne Daemonkin codex is 5 points more expensive and Possessed don't even need the icon; they have all the benefits already built in.
Necessary to the success of this unit is transportation. Options are rhinos and land raiders. I hate land raiders, especially chaos ones, why oh why can't I get the flamestorm cannon variant? Lets not go there just yet.
A bare bones unit clocks in at 185 points with a basic rhino. I am not sure of I want to add anymore models but 5 are sturdy enough. Run them up the board, flat out, and ram them down some poor soul's throat. Not much more than that,just point and click.
One tactic I favor is, on the turn before assaulting, disembarking the models without moving the rhino, and in the shooting phase moving the rhino flat out to block line of sight. This lets our possessed weather the enemy shooting phase, gives opponents a road block to walk and assault around, and if the rhino dies another blood tithe point is earned. In other cases where the models can actually shoot something be sure and shoot them first before moving the rhinos flat out. Don't forget their mutation table, strength 6 on the charge, and counter attack.
Thankfully I had some possessed from a long time ago, never assembled and waiting for this moment. The aesthetics of the models are actually quite pleasing. Before adding these models to your collection consider a kit bash or the Gal Vorbak from Forgeworld. Those models are super nice and can double as a very powerful unit in a Word Bearers heresy list.
These guys aren't that bad. Try them out, run them up, give them feel no pain, and earn those blood tithe points!