From 1d4chan
Before there was the Emperor of Mankind, before there was an Everchosen, before there was Kharn, there was Arbaal.

Arbaal the Undefeated is one of the original Chaos Champions from the earliest editions of Warhammer Fantasy Battles. A sworn servant of Khorne, he is perhaps the greatest champion of all those dedicated to the Blood God; thousands have fallen before his axe, and none have ever conquered him. As signs of favor, Khorne gifted Arbaal with the Hound of Khorne, a monstrous Flesh Hound that serves as his steed, and infuses him with tireless energy for the slaughter. Yet, the boons come with a price: should Arbaal ever flee from battle, then Khorne's wrath will be unsurpassed.

In crunch-terms, he rode into battle upon a mega-nasty steed that was immune to magical weapon attacks and made them both immune to spells; he traded the usual Frenzy rules of the time for Destroyer of Khorne (2D6 Strength 6 Weapon Skill 9 attacks each round), and if he ever fled combat he would instantly turn into a Chaos Spawn. Am I safUIYSFDBOAYDBGASDYLAWADIS*FWIP* He only came with chaos armor and an axe, but this was the edition when special characters could buy extra gear to pimp themselves out.

Arbaal was rumored to return as the Khornate Lieutenant of Archaon as part of the next release for The End Times; while he does indeed return, he gets killed by Caradryan, Incarnate of Fire. So much for the Undefeated.

The Champions and Lords of the Warriors of Chaos
Aekold Helbrass - Arbaal the Undefeated - Archaon - Asavar Kul - Beorg Bearstruck - Bödvarr Ribspreader
Dechala - Egil Styrbjorn - Egrimm van Horstmann - Festus the Leechlord - Feytor - The Glottkin - Gutrot Spume
Haargroth - Harald Hammerstorm - Lord Mortkin - Kaleb Daark - Kayzk the Befouled - Krell - Maggoth Lords
Melekh - Mordrek the Damned - Sayl the Faithless - Scyla Anfingrimm - Sigvald the Magnificent
Skarr Bloodwrath - Slambo - Styrkaar of the Sortsvinaer - Tamurkhan - Thorgar the Blooded One - Throgg
Valkia the Bloody - Valnir - Vardek Crom - Vandred - Vilitch the Curseling - Wulfrik the Wanderer