What if you wanted to create a group of villains serving a Dark Lord? You want the characters to be powerful, but certainly not invincible, a realistic group, but also disparate enough to be far from united. It's a fine line.
Here is a copy of the presentation I gave at JordanCon 2015 on the creation of the Forsaken, a group of just such villains. Like so much of Jordan's work, they had a solid grounding in reality.
For further reading, there is my essay Three Strands Common to the Forsaken which predates this presentation.
I have written detailed analyses on eight of the Forsaken: