The White Flash
The White Flash is a Chaos Warband responsible for the death of numerous planets. The Alpha Legion uses them as a team to destroy the government of systems ripe for invasion. Here is how the average White Flash attack goes.
At night, just before the target leaders leave their offices or euivalent buildings an explosian causes the structer to come crashing down. The fingers of the flash, an elite demolition teams reveals themselves, opening fire with their bolters and laughing at the pathetic forces sent to stop them. As more enemies show up the next wave, the knuckles set in. A rhino full of Combat Flash teams drives into the enemy city or camp and sets about with ripping the defenders to pieces. With a perimeter secure the combined teams look for the enemy leaders who may have survived the initial explosian they swiftly gun them down and leave two things in their wake. A teleport homer and an icon, they all then board the rhino and head to an air field to escape back to their strike cruiser. The next day, as planetary defense forces look for the cause of the devastation the icon, when touched explodes into a mighty demon prince while the fist falls, a chaos terminator squadron lead by lord Krevis assaults the enemies, a short but bloody battle follows, and with a strong foothold on the planet the Alpha Legion invasion begins.
This would be an apocalypse force with the demolition specialists being chosen and the assault specialists being bezerkers or poseassed.