After I began writing my series, I decided to type some of the names into Google. I found that the name of one my characters (Trent Steele) was used in an episode of The Simpsons. I also found that a faction (The Brotherhood of the Shadows) was in Mortal Kombat. If I am not using traits from either of them, would I be able to have them in my books without an issue? I did not know about these until I looked them up.
There are probably lots of names and titles that are coincidentally repeated in multiple books. To take a silly extreme, if someone tried to sue saying "He had a character in his book named John, and I have a character in my book named John. He's stealing my character name!", I can't imagine the courts would let that go very far.
You can own a trademark in a name. I am not a lawyer, but I'm pretty sure that if you wrote a book about a boy with magic powers named "Harry Potter" you would lose a trademark suit pretty quickly. But a writer can't claim trademark to the name of every character in a story, every made-up place, etc. Especially if your character has no obvious relation to theirs.
The more commonplace the name, the harder it is to win a trademark suit. I recall when I started a business a few years back I did some checking on trademarks of business names -- not the same thing of course but it's covered under the same laws -- and they said that made-up words have the strongest protection, descriptive phrases the least. Like if you started a business and called it "Fracnoblag" -- a word I just made up -- you'd have a strong case if someone else started a business with the same name. But if you call it "Main Street Auto Repair" and somebody on Main Street in another town uses the same name, your case is very weak. By analogy, I think if you wrote a story with a character named "Aragorn" you'd be in trouble. But "Henry Smith"? No problem.
BTW LaurenIpsum mentions "James Bond". Ian Fleming did not invent the name "James Bond". There was a James Bond who wrote books about birds, and Fleming just liked the name and so used it. https://en.wikipedia.org/wiki/James_Bond_(ornithologist) You could probably make a case that his trademark claim is weak because of that. Not that I'd try it, I'm sure the publishers can afford better lawyers than I can.
Within reason, if the name itself is not already instantly recognizable (Bart Simpson, Lara Croft, James Bond), you can probably get away with using it. "Trent Steele" may be generic enough.
Similarly, there are only so many variants and arrangements of organization and darkness, so whatever you come up with has probably been used or alluded to elsewhere.
In order to avoid charges of plaigiarism, make sure your Mr. Steele and Brotherhood are different enough from the ones you Google that readers would not easily confuse them. You might do this by changing your character's gender and/or race, and making your organization's name less mustache-twirlingly evil.