The manga/anime series "Death Note"

It's a long mental battle between two clever people, not much for rationality techniques, but characters think rationally, and the magical parts have well defined rules, similar to Lawrence Watt-Evans' fiction.

I would be terribly thankful to anybody who could reccomend me some more stories involving these sorts of fights. Trickery and betrayal is common enough, but a prolonged fued of this nature is rare.