Sometimes the simplest customs are the most effective. My "Vampire Assassin" uses only a few parts that are simple swaps, but the end result is something i am very happy with.
The figure itself is just a Black Knight Legion Builder. The head is from a Carpathias and the robe is from a Star Wars Black Series Kylo Ren. I cut that robe down the middle so it was more of a cape and slipped the figure's arms through the holes to create my hooded look. I also made two small holes in the hood for his vampire ears to pop out of and added a few black belts from a Coliseum Orc. Again, super simple, but for a really nice payoff!