Khorne
The god of blood and skulls. His worshippers are raging bersekers, seekign to spill blood and take skulls in the name of their god. They slaughter all they come across, from the bravest soldiers, the purest innocent, and even each other. It does not matter from where the blood flows, only that it does. To them, all living creatures are just bags of blood and bones to be slaughtered without mercy.
Tzeentch
The forces of Tzeentch are a confusing and irritating bunch. Their lord, The Changer of ways, is a cunning and crafty one, preferring subterfuge and complexity in lieu of simplicity and directness. They are also proficient sorcerors, with Tzeentch himself being a god of magic. They are held back by the often conflicting, contradicting, and even self-defeating nature of their god, who follows his whims as often he does his meticulously crafted plans.
Nurgle
The vile and disgusting Nurgle is a god of rot, disease, and plague. He concocts the most horrific and virulent illnesses in his garen of plagues and infects his immortal followers with them, having them wander the galaxy to spread his 'gifts'. This diseases are the worst in all of the galaxy, targetting not just the body, but the soul, turning even the purest of humans into horrific ghouls hellbent on further spreading their sickness.
Slaanesh
The youngest of the four. Slaanesh is the god or goddess of all forms of excess, whether that be pain, exctasy, grief, or pleasure. She and her followers seek any method to achieve higher highs and lower lows, from the loudest music, the most toxic drugs, the most twisted orgies, and the most sadistuc slaughters. No act is too sacred or taboo, everyhting is permitted as far as he and his followers are concerned.