The Alpha-level Motherfucker, Chaos Ghost Rider, Captain Supreme Ass-Fucker. The Lord Discordant is known as one of the most badass motherfuckers ever put on tabletop. Abaddon has nothing on this badboy when it comes to the cool factor. Yes, the Lord Discordant's model really is awesome and badass.
What makes the Lord Discordant so exceptionally badass (other than the bitching cloak) is that they have their own personal Daemon Engine mount on which they ride around and play horsie whilst their combined mere presence is able to short-circuit machinery, shut down augurs, cause servos and actuators to fail, and corrupt Machine Spirits. Their Helstalker mounts use Magma Cutters to forcibly slice open a vehicle they have pinned while their enormous Hypno-Armour Syringes inject scrapcode and Daemonic dataphages directly into the machine's circuitry. Should the need for close combat arise, the Lord Discordant himself lunges forward with a massive Impaler Chainglaive and Mecha-tendrils.
The Daemon Engine hungers for the Motive Force and once it NOMNOMNOMs this essence, this harvested energy is then used to reinvigorate other Daemon Engines, or is released as beams to infect the systems of other vehicles. Even after the foe has been beaten, a Lord Discordant continues to prowl the battlefield, searching through wreckage for a sliver of Motive Force that may remain. When such remnants are found, their energy is swiftly cannibalized. Captured Machine Spirits are ceaselessly experimented on, twisting them into myriad data configurations for different interesting effects. In terms of function, it is quite similiar to the Dark Eldar Medusae, just replace the psychic life force with that of mechanical life force.
Lords Discordant are found across the entire Chaos pantheon. Those lords devoted to Khorne make motivators seethe with burning rage and transmute lubricating oils to blood. Tzeentchian Lords Discordant cause vehicles to twist themselves through unseen dimensions, crumpling them into impossibly small heaps of slag. Nurgle Lords cause vehicles to vent internal gases, while their outer plating sloughs off like a diseased scab. And then, of course, we have those Slaaneshi Lord Discordants who are able to rewire machines to feel constant and excruciating pain, so that it will feel bad when they make sweet, sweet love to them.
The reason Lord Discordants chose that name is because Discordant is something of a horror story among Adeptus Mechanicus. Discordants are pretty much like Blanks, except for technology instead of psychic power. They're extremely rare mutants that for some reason only get born on forge worlds. Anything more advanced than a knife slowly breaks in an aura around Discordant, and the more advanced tech is the faster it breaks. Most times this leads to infant Discordants killing themselves, their family and few thousand people around them when they accidentally break the air recycling machinery in their hub block. Those few who survive are then hunted down by Skitarii and killed as an affront to Machine God. Still, some manage to survive, mostly by fleeing into wasteland outside forge cities, and cogboys are justifiably afraid of them, as they grow more powerful with age to the point of instantly frying anything high-tech in their auras, killing any tech-priest that replaced at least one vital organ with bionics (which is most of them). The irony is, if any Lord Discordant were to meet actual Discordant, the former most likely would die instantly, as his bionics and implants burn out.