Today's thoughts, WarHammer Fantasy, Mark of Chaos

I've watched this video a long time ago, well, I feel like talking about it a little, as it is one form of inspiration for me to start my first WarHammer Fantasy army, and I've decided to go with Warriors of Chaos. I've also been a long devotee of Nurgle, but a little fan of Khorne, so I will mix this 2 chaos marks in my army.I just don't understand one thing though, how do like 20+ Chaos