I hate to be "that guy," but that's not the proper grammar for The Black Sword in Latin. Nigri is plural while Gladius is singular. The proper grammar would be Niger Gladius, or Nigri Gladii (The Black Swords) if you want it to be plural.
Sorry. I currently take Latin in school, and I hate to see someone use the language incorrectly.
English
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That's good to know, actually, as I figured Google Translate was wrong (like always). So thanks for being "that guy".