Vardek Crom
Vardek Crom the Conqueror, Herald of Archaon is a unique Chaos Lord of Chaos Undivided created as part of the build up to the Storm of Chaos campaign. He is one of the Lieutenants of Archaon, and the most feared and powerful of them all, to the point he received his own custom rules to allow him to be used as a character in his own right. He first appeared in the Warhammer Chronicles of White Dwarf #282, and his rules were reprinted in the Storm of Chaos army book. After this, he languished until The End Times, when his stats got reprinted with some slight tweaking in "Nagash: Book 2", though the fluff in "Nagash: Book 1" states he officially gets himself killed off via an acute case of Valten delivered hammer applied directly to the forehead.
The Legend
A member of the Kurgan tribe known as the Kul, Vardek Crom took control of his people before he was twenty years old by killing the previous chieftain. Haunted by visions of a mighty warrior who would unleash the final dominance of Chaos over the world, Crom brooded: was this a vision of his destiny? Or was this a warning from the Gods that there was a champion out there even mightier than he?
He received his answer when Archaon and the Swords of Chaos crossed into his land as part of Archaon's search for the Six Treasures of Chaos. Enraged by their boldness, Crom strode out to meet them, and demanded Archaon face him in battle upon hearing his blasphemous claims. Archaon's warriors interposed themselves, but Crom cut down fourteen of them effortlessly before Archaon finally deigned to face him himself. The Everchosen defeated the Conqueror effortlessly and revealed to him the Sword, stopping Crom dead in his tracks. Of the Treasures, Archaon had three; the Sword, the Mark and the Eye, with only the Steed, the Armor, and the Crown remaining. He invited the mighty Kul to join him in his quest, and the humbled king agreed. Since that day, Crom has been Archaon's most loyal follower, roaming far and wide at Archaon's side and beyond, the self-proclaimed Herald of the Everchosen.
On the Tabletop
In the game, and in the edition he was written for, Crom the Conqueror is a damn melee beast. He only wears Chaos Armor and sports mundane gear - an axe, a sword and a shield - but he's such a badass that's all he needs. He specializes in both cleaving through ranked infantry and countering enemy characters, so the trick is knowing when and where to put him.
For 230 points, Crom uses up a Lord slot and he has to be the army's general unless Archaon is present; Crom bows to one master and one master alone. His statblock makes him a killing machine: Movement 4, Weapon Skill 9, Ballistic Skill 3, Strength 5, Toughness 5, Wounds 3, Initiative 8, Attacks 5, Leadership 9. However, it's his special rules that really make him as a character.
Master of Chaos Undivided: Remember, this was the edition in which Chaos Undivided had the most emphasis, up to and including its own mark. Chaos Warriors and Chaos Knights bearing any of the four Marks of "Chaos Divided" (Khorne, Slaanesh, Nurgle, Tzeentch) count as Special slots, whilst Chosen versions of the aforementioned and all Daemons count as Rare slots. On the plus side, your Marauders and Marauder Horsemen units all get the Mark of Chaos Undivided for free, which is handy, since they're the cheapest unit you have in this sort of army and they have the suckiest Leadership, so that free reroll is useful.
Immense Pride: Pretty standard for a character with Crom's fluff, Crom has to accept any challenge he is offered. Since he specializes at nullifying enemy characters, this is precisely what you want him doing anyway.
The Way of the Warrior: The big reason you're picking Crom, this rule allows Crom to swap between sword and axe style or sword and shield style whenever he wants, by declaring so at the start of each round of combat. Each style has its own special advantage in a challenge.
- Sword and Axe: +1 Attack in general combat, but in a challenge, Crom gets to make an extra attack for each wounding hit (before armor saves are made) that he lands. This allows Crom to scythe down a high health opponent, if he needs to kill something dead fast.
- Sword and Shield: +1 to Armor save in general combat, but in a challenge, Crom nullifies all special rules applied to his enemy's gear, mundane or magical. Yep, that's right; no matter what your opponent counts as wielding elsewhere, in a challenge with Crom using sword 'n' board style, they count as just using a single hand weapon. This is the style pretty much everyone uses in a challenge with Crom, since it makes him the ultimate stone wall.
- Do note that while this makes him crazy powerful, he's not going to beat everyone with either of these styles despite his statline and insane rules. As a quick example, in the lore he tried taking on Ungrim Ironfist's forces, but if you pit him against the Dwarf in a fight he'd get his shit kicked in. He's more of a bully, picking on anybody who has a weaker statline but when faced with anyone who has as good a statline (or better) he'll fall to pieces, especially if they have a Ward Save or other special rules of their own.
When revamped in 8th edition, he lost Master of Chaos Undivided and traded it for Eye of the Gods, Immense Pride specifies that in any unit containing Crom and another Chaos Warrior with Eye of the Gods it has to be Crom who always answers or issues challenges, and Way of the Warrior got seriously nerfed. Now, sword & board style gives +2 to armor save and a 5+ ward save from parry, whilst sword & axe style gives him +3 extra attacks instead of the normal +1. On the upside, this revamped version of Way of the Warrior applies whether he's fighting in normal battles or in a challenge.