Chaos Spawn
The Gods blessed you too much, and now I shall end your misery! Such a fate does not await me! - Thorgar the Blooded One, on the you-know-whats
The Chaos Spa-, ahem, the unit in question are considered by many to be the worst unit in any Chaos army book and, quite possibly, the entire game of Warhammer (the Space Pope coming in a close second). They are so bad, in fact, nobody takes them, even for flavor or joke games, and that to even utter their name causes a horrid mutation turning you into a Chaos Spawn yourself. Wait! No! I didn't mean it- *OHSWEETJESUSMOTHEROFGODNOOOOOOOOOOO!!GLARBLBLBLBL*
Ahem... Continuing where my predecessor left off, you-know-whats should only be referred to as you-know-whats. That or they-who-shall-not-be-named.
In fluff, aspiring champions of chaos normally devolve into said units for any of the following reasons: if they use chaos for their own gain, their patron God thinks they're not worthy of their favor, they can't handle the sheer amounts of mutations they go through during their ascension into a full-fledged champion, or, you know, it's Tuesday and Tzeentch is feeling bored since there's not a lot of "Just as Planned" going around. When this does happen, Chaos Spawns devolve into no more than mindless heaps of mutated flesh who attacks anyone near them and eventually die after a short period due to their unstable form and..... oh shit, I said it, didn't I? No.....NOOOOOOO! GLARBLRAWRGLARBL
Only Failbaddon can comprehend how truly goddamn useless these things are. Generally by looking in a mirror. Khorne only knows why he hasn't been turned into one yet.
The most significant Chaos Spawn in Warhammer is Scyla Anfingrimm. The only Chaos Spawn who yet has the favour of a god.
Game Play
You-know-whats are horrible in-game. Coming in at a whopping forty points (That's almost three normal CSMs) they wander around the board aimlessly with a throw of the Scatter Dice, are Slow and Purposeful (which doesn't count as difficult terrain anymore), have the Rage special rule and die to Bolter fire earning your opponent a free kill point. They fucking suck, essentially. There is considerable evidence that they were originally supposed to have the Feel No Pain rule, ergo making them marginally useful, but sadly the Codex, through a series of misprints, lacked this.
Phil Kelly remembered that under that mass of writhing limbs and stupidity, there's a Chaos Space Marine, so brace yourselves for a shocker: they're not absolutely worthless anymore. New features include...
- A lower point cost (30, as opposed to the previous 40).
- Causing fear while being fearless themselves.
- No longer moving randomly or at a goddamn crawl. In fact, they move as fast as Metal Bawkzes and do not give a shit about terrain.
- Rage now meaning that they get +2 attacks on the charge, making it actually useful.
- A D3 roll every turn that determines what mutation they get for that turn. They can get a 4+ armor save, a roll of 2D6 for their number of attacks (you pick the higher one), or poisoned attacks (at 4+ to wound).
Their stats are otherwise unchanged, so holy shit, it's almost worth taking two or three of them and throwing them headlong at the enemy as a multi-wound distraction to soak up fire for you. Almost. Okay, that is not true. 30 points for a model with 3 T5 wounds that can move 12", has useful special powers, can be taken in squadrons and can become T6 with Nurgle is frankly excellent. Unless you run into Grey Knights, for whom the Spawn is just a mild annoyance.
The other way they are useful (aka you need them now)
In the new Chaos Space Marines Codex there's a table, like the one in the Warriors of Chaos Army book, on which your HQ, when killing an enemy character (keep in mind: not IC, just C). It's a 2D6 table with some of classics: +1S, +1T, +1W...
But one of the results... forces you to swap your awesome super killy Chaos Champion with... err, the-one-which-shall-not-be-named! So now you have to buy a box of these sick horrors in order to play.
RAAAAAAAAAAAAAGH! GW! WE WILL COME TO NOTTINGHAM AND HANG YOUR MISERABLE BODIES ON THE FUCKING WINDOWS OF YOUR OFFICES WITH YOUR BLOODY GUTS!
No Phil, you shall not worry, we know it's not your fault. I promise you'll be fine.
- and just then, a heavy Norscan accent pierces the air*
Oh shut the hell up you fucking newfags, 'bout time you had to deal with this anyway.