No it isn't, at least not in the Untied States. Under current US copyright law names, titles, slogans, logos , mottoes, and common words/phrases are not eligible for copyright protection. Under certain circumstances however they can be registered as trademarks
Bellator Mortis
The phrase was copyrighted by Ro Mathew, not Bensy Idiot Boban.
Vampire Knight manga is copyrighted. You can purchase it legally from Amazon.
A catchy phrase is a phrase in business like "Posture Power"(copyrighted already) or something like the Ross store: "dress 4 less"(copyrighted already)Yea, you get the idea
Cavaliere di morte is an Italian equivalent of the English phrase "death knight." The masculine singular noun, preposition, and feminine singular noun translate literally into English as "knight of death." The pronunciation will be "KA-va-LYEH-rey dee MOR-tey" in Italian.
can a phrase be copyrighted? No, it can not. You are allowed to say it, just be careful not to make it the moto of your ice cream bars. :)
No
You could say 'shi no kishi,' written: 死の騎士
Death = θάνατος (thanatos) Knight = ιππότης (ippotis) Thanatos Ippotis is a rough translation for Death Knight
The phrase "the dark knight" is a nickname for Batman.
there is no literal translation to associate with the meaning of death knight.
No, the Death Gate is only for the Death Knight that created it.