I've about got my Iron Hands where I want them - so of course next up is "what do I want to do with my Alpha Legion?"
There are a couple things I want to build around, after talking to friends, looking at the 'net, and reading various things.
First up - the previously-maligned Chaos Posssessed, and in a later post, the Lord of Skulls - because it got a cost cut.
So first up - the 'free hugs brigade', AKA Chaos Possessed. Why? Because throwing twenty durable jerks across the field into the enemy's lines on the first turn is FUN, that's why.
First question - why not Berserkers? I'll go into it a little later, but the short answer is going to be durability. 'serkers are going to crank out a stupid volume of attacks, but aren't going to be nearly as hard to clear off the board after the charge. Trust me, twice the wounds and a potential extra -1 to hit is a big deal.*
Possessed are a bit bulkier than the average marine. They have a nimble 7" move. They'll hit you at S5, AP-2 on a 3+, and they'll do it 1d3 times. With respect to durability, they've got two wounds on T4 with a 3+/5++. You can bring up to 20 in a unit, and you can pick whatever Mark of Chaos you want.
So on average, a Possessed will swing twice, hit on a 3+, and then wound most infantry on a 3+. Base strength 5 means you'll wound all vehicles on a 5+, and when you manage to wound - they're probably looking at a 5+ armor save or so. This is a decent start.
So you're a melee unit - this may simplify the support side of things. Possessed have the DEMON keyword, they're INFANTRY, and they have their pick of the four Chaos Gods.
First up - the Greater Possessed.
Bringing one and keeping it close to your Possessed unit bumps them up to S6. S5 to S6 is a significant bump vs T3 (light infantry), T5 (bikers, lightweight vehicles) and T6 (most vehicles). It's almost, but not quite, +1 to wound. As a bonus, this guy is a little more accurate and cranks out damage 1d3 attacks.
Second - The Dark Apostle
He's the new guy on the block, and he's got some good stuff in his book. You were going to bring at least one Battalion in 2k anyway. This guy and his two friends with a book mean you get your prayer off at the start of the round on a 2+, which is pretty reasonable.
The default prayer is 're-roll misses in melee' so if you get down-range close to your new friends, you're probably using that. 3+ with a re-roll bumps you from 66% accuracy to ~88% accuracy, which is noteworthy.
Benediction of Darkness is your money-maker here - it's a -1 to hit vs. ranged attacks. If you go second, your nasty melee boys are easily going to be at -2 to hit.
Soul-tearer portent isn't bad, per se - it's worth +1 to wound - but you're giving up the -1 to hit. You have to get into melee first, which means being alive to move and assault.
Also, honestly - I'm skipping the Litany of Despair (morale isn't always super-relevant, and making the enemy Fall Back out of melee is just fine) and the various self-buffing power of the apostle because frankly, if I wanted a beatstick, I'd take a beat-stick, not a buff-bot that can double as one.
Third up - Psychic Support
We're chaos, we have good psychic powers - we should bring them. The Dark Hereticus discipline is a lot more useful for assaulty units. There are powers that you get access to with Marks, and some regular powers. The Dark Hereticus discipline at least offers options with respect to psyker choices. I would suggest Warptime and Miasma of Pestilence at a minimum. The biggest challenge here is prioritizing the powers.
Warptime - I feel like this is a no-brainer, but moving another 7" for free is pretty useful. I'd say this is probably the most important power - you have to get into melee. 14" move plus charge is probably going to get you there.
Miasma of Pestilence - If you're willing to take the Mark of Nurgle on the sorcerer and the Possessed, you can grab another -1 to hit. Hello, durability. This one works all the time, unlike the Alpha Legion trait. If you REALLY want to be a jerk, stack this with the Dark Apostle's prayer for a -3 to hit vs. ranged attacks (or -1 in melee, which still matters).
Weaver of Fates & Delightful Agonies - note that all the god-specific chaos powers help durability. Weaver of Fates means you take the mark of Tzeentch and can get up to a 4++, whereas Delightful Agonies means you take the mark of Slaanesh and get to ignore damage on a 5+. Neither of these are bad powers, per se - however, you can stack the to-hit penalties as Alpha Legion and I'd rather play to that synergy. Also, math-wise, I'd rather mess up hit rolls - the earlier you screw up rolls, the better it tends to play out.
Diabolic Strength - +2 strength, +1 attack. You're an assault unit. This is kind of nice, obviously. Between this and the Greater Possessed, the regular Possessed is hitting at S8 - which is awesome. You wound Marines on a 2+, you wound most vehicles on a 3+, and you're wounding the heaviest of armor on a 4+. If you really need your possessed to mess up a Knight, Land Raider, or something else, there's Veterans of the Long War.
On Death Hex and Prescience - look, these are legitimately good powers. Death Hex doesn't do quite as much for a -2AP weapon (outside of something like Terminators w/ Storm Shields, most of the time your invuln save is a fair bit worse than your armor save). Prescience is solid, but you still want to get there - Warptime and Miasma of Pestilence do that for you very well.
Regarding the Master of Possession
This guy gets an honorable mention - if he can keep up with the Possessed, he could theoretically give them +1 to their invulnerable save (via the Cursed Earth power) and give them an aura of 're-roll 1s to hit and wound (via the Infernal Earth power).
If you're taking one psyker - it's definitely a Miasma/Warptime guy. If you're taking a second one - either you're going with Prescience/something else to buff whatever, or this guy is running along behind the Possessed blob and buffing them. Note that if his powers go off, he's basically giving you Weaver of Fates while pretending to be a Chaos Lord, AND he's somehow a Lieutenant for that unit.
There are a handful of stratagems you'll care about for your Possessed and their supporting models.
Veterans of the Long War - you know it, you love it. +1 to wound for a phase. Be aware of it if you need it.
Grandfather's Blessing - eh, if you decided you like the Nurgle approach for durability, you could pay 2 CP to get a guy back or heal a wounded one. I don't think it's going to be that useful on the regular, though.
Chaos Familiar - Keep this in mind if you think you messed up on a supporting psychic power. Or if you want to economize - remember that you can trade Smite out for a supporting power for one CP. Alternatively, if you want to take a Demon Prince and want two support powers, this is how you get it.
Fury of Khorne - if you skipped out on all the durability-enhancing options by taking the Mark of Khorne, you can fight twice. Note that if you got a Warptime-enhanced charge off and you daisy-chained a large unit together, it won't be hard to outpace your support.
Forward Operatives - We're Alpha Legion here - we set up away from everyone else. Not bad, but remember to stay near that Dark Apostle and Warp Time psyker.
First off, remember that "I Am Alpharius" is funny, but more of a trap than anything.
Master of Diversion - you can redeploy three models. This is a nice, tricksy little trait - but note that your core module has several components - the Possessed, 1-2 support psykers, a Dark Apostle & book carriers, and a Greater Possessed for a total of 6-7 pieces. You can daisy-chain a large unit of Possessed, but you'll have to think about who has to start near whom (the Dark Apostle & friends) versus who can afford to advance (everyone else but the Possessed, really).
Alternatively, this can always be used to redeploy other supporting aspects of your army as well.
Most of the rest of the Alpha Legion traits aren't bad, but they also don't scream out to support the Possessed blob like Master of Diversion can.
What Do We Start With?
At this point, I'd say the smallest version of the Possessed starts with a Battalion that looks like this -
Chaos Sorcerer with Jump Pack
-bolt pistol/force sword
-Mark of Nurgle
-Miasma of Pestilence
Dark Apostle w/ Benediction of Darkness
Greater Possessed w/ Mark of Nurgle
20 Possessed Chaos Marines w/ Mark of Nurgle
2 Dark Disciples
You have the possessed blob with the ability to go up to -3 to hit on turn one, and -1 to hit subsequently. You've dropped around 700 points on this module.
You're not done, though - and neither am I. At this point I've got the ability to get the Possessed down the table, between Warptime, Miasma of Pestilence, and Benediction of Darkness. I've got the no-brainer Greater Possessed in there - so I've got to figure out what more killy support I want in there. It may be another jump sorcerer with Prescience and something else - it might be a demon prince with re-rolls and prescience, or it might be a cheap jump lord with a thunder hammer.
What else do we need?
We need guns. We need to be able to clear a screen on turn one - it's a waste to dump a huge unit of choppy fiends into the scout squad, cultists, or guardsmen standing in front of a juicier target. Chain cannons, Obliterators, and Noise Marines come to mind as options.
We also need more threats - that's not going to be hard to do with another ~1300 points available to spend. Regardless of how many wounds and the minuses piled onto the Possessed, they can't be the sole threat in the army.
I'm going to stare at a spreadsheet and offer some brainstorms - I feel like this is a reasonable starting point for a list around Possessed, as it's got the basic building blocks and the logic behind them.
*Why Not Berserkers? It's Math
To keep the math easy and demonstrate differences, we're going to go with boltguns and chainswords here, with no re-rolls to hit or wound, standing in the open. Yes, AP makes a difference (once AP gets more than -2, the Possessed have a marked advantage because of 5+). Damage makes a difference if it's 2+, since the Possessed have 2 wounds.
Berserkers are -2 to hit 20 wounds vs. shooting. Just 20 wounds vs. melee
I need 360 boltgun shots to kill the 'zerkers. (360 shots hit on 5+, 120 get through. 4+ to wound mean 60 wound. 3+ save mean 20 wounds go through, squad dies.)
I need 180 chainsword swings to kill them. (At melee range I hit on 3+, so 180 swings means 120 hits - I wound on 4+, so I get 60 wounds. They fail on 3+, so I get 20 wounds through.)
Possessed - I'll do shooting twice - with and without psychic buff.
WITH Miasma - You need 1,440 boltgun shots from marines. (They hit on 6s, so they get 240 hits. That turns into 120 wounds, and Possessed 3+ armor means that they take 40 wounds and die).
WITHOUT Miasma - You need 720 boltgun shots
Possessed melee - we'll factor in Miasma here because you almost certainly had a chance to cast it -
I need 480 chainsword swings hitting on 4+. (They hit on 4+ - that turns into 240 hits. Wounding on 4+ turns into 120 wounds, and 40 of those get through the 3+ armor).
What I'm saying is this - they're not just twice as hard to kill. And the long they're on the board killing stuff and tying up enemy assets, the better.