Fictional adventurer created by pulp writer Robert E. Howard. Though Howard was best known as the creator of Conan the Barbarian, Kane was certainly his most unique character, a dour, near-humorless 17th century swashbuckling Puritan swordsman. He made his first appearance in a story called "Red Shadows" in the August 1928 issue of "Weird Tales."
Kane, with his black outfit, slouch hat, and arsenal of swords, pistols, and muskets, roamed throughout England, Europe, and Africa on a compulsive and never-ending quest to fight evil and rescue the innocent.
One of Kane's weapons was a juju staff that protected the bearer from evil. It was given to him by N'Longa, a near-immortal African shaman who ended up becoming one of Kane's closest allies. It was later revealed that this was no mere enchanted staff, but the actual Staff of Solomon, which was actually a great deal older than the King Solomon that it was named for. In fact, it was described as being older than the Earth and capable of incredibly powerful magicks.
In a long series of short stories, poems, and story fragments, Kane fights his way through bandits, pirates, cultists, African tribesmen, monsters, sorcerers, ghosts, psychotics, vampires, slave-traders, and more. He beats some of them by being smart, some of them through dumb luck, some of them from his truly breathtaking fighting skills, and some of them just by being an almighty mean son-of-a-bitch.
Many of the stories are pretty shockingly racist, with Kane fighting his way through hordes of savage, inhuman Africans preparing to sacrifice noble blonde European maidens. This is somewhat alleviated by the inclusion of Kane's friend N'Longa, who is as brave as and probably a great deal wiser than Kane, as well as a few other African characters who ally themselves with Kane on his quests, but on the whole, the stories read a lot like other fiction of its era -- white people as the heroes, non-whites as either depraved villains or comedy relief. It doesn't mean the stories aren't still fun to read -- but ya gotta know what to expect going in to 'em.
Why do I like these stories? Part of it is that Howard wrote such rollicking action. The man was a genius in envisioning and describing thrilling action, excitement, and suspense. His fight scenes are absolutely enthralling, and there's nothing vague about what's going on -- he's got every participant mapped out, he knows what everyone is doing, and he knows how to tell you all that while still making it fun to read.
Most importantly, Solomon Kane himself is just a wonderful character -- a gaunt, grim-faced Puritan with such a mad-on for evil that he wanders the world fighting monsters, pirates, cult-leaders, and vampires with a rapier and pistol. Think of it as Johnny Depp playing a Pilgrim in the "Pirates of the Caribbean" movies. Kane's character simultaneously embraces stereotypes and then breaks them in a way that makes him one of the most interesting individuals in fiction.
If all you know of Robert E. Howard is the Conan movies or comic books, you should check out the man's stories -- when I read my first Howard story, I was expecting something dumb and thundering, like the first Conan movie. But Howard really was one of the finest and most skilled writers of the pulp age. You should enjoy his books and stories for yourself.
Solomon Kane has also appeared in a couple different comic book series, and there's a movie about him in production.
Some research from Wikipedia, most from reading the books