As far as I know, both Conan and Solomon Kane are public domain in the US, and the rest of the world. But yes, the trademarks are closely guarded and their visual interpretations are probably under copyright (though, you can do your own interpretation based on text description). If you fear the machine behind Conan, there are tons of PD alternatives (Herclues, Ben Hur, etc.). There are a number of ghost hunter characters, but not a lot of monster hunters like Kane. Closest I can think of is Mr. Monster and Detective Bently of Scotland Yard. Though, Bently's monsters always turned out to be human criminals in disguise, like Scooby Doo monsters...