For
legendland, we had to recast five characters from Legend of the Seeker. I had a few ideas I wanted to do, but I ended up recasting with Marvel characters. I could have gone for appearances, but I preferred to go for personalities.
For Cara, it was an easy choice. Someone who was conditioned and made special to work for her government? Someone who was highly skilled in many areas, including fighting and interrogation? Someone who had switched sides and was working for the side of "good" now, balancing out what she had done before? Cara is Natasha Romanoff.
For Richard, I went with Thor. He's someone who (at least in the second movie and the comics from what I've seen) is just good. He's the type that I could see rescuing kittens, just as we always headcanon that Richard does. He also can be impetuous and is more blunt rather than manipulative, which I thought served Richard well.
For Darken Rahl, I went with Loki. I liked the idea that they would still be brothers in this recast, but it was more than that. Loki's morals are much more slippery than Thor's. He is willing to do what he thinks he needs to in order to get what he wants. And what he wants is power. He also is very skilled at magic and deception and is charismatic, all traits I thought also applied well to Darken Rahl.
I had originally considered casting Wanda Maximoff (the Scarlet Witch) as Kahlan, but I would only have had comics pictures of her which wouldn't work with the others being live action then I thought of Jane Foster and decided I liked her better. Partially it works because Jane and Thor are a couple, one that has had to overcome some major obstacles. But a lot of it was just due to Jane being so rational and curious. She always wants to know everything and figure everything out. She is a balance to the emotional nature of Thor, just as Kahlan helps to balance out Richard.
I thought of Heimdall for Chase, due to the protecting the bridge/boundary, but then I decided I prefered Rhodey. Rhodey is still a very protective/defensive character, but he also expands out to help in other ways. While Chase was mostly just protective in the show, he did have a more expanded role in the book, and I liked Rhodey for that.