Board Thread:Questions and Answers/@comment-24.62.142.87-20140331201702/@comment-6697950-20150429181738

By quoting taking out of context, I meant that you quoted without explaining in what circumstances the sentence was used. I hope you don't expect me to quote all the posts that were written before my reply for you to understand the context of my words. "Context" in this case refers to what the talk was about before my post and the rest of my post that might have explained what I had in mind. I.e. by "taking my words out of context", I meant that you only quoted a part of my sentence and interpreted it as you wished, when the other parts of the post might have indicated that I was referring to something other than what you had in mind.

Truth be told, I tried looking for the post that you are referring to and no, I can't find it on any topics related to Excalibur. The best I was able to find was http://swordartonline.wikia.com/wiki/Thread:44313, but I couldn't find your "quote" there either. If you want to continue this talk about context, I would like to ask you to link me to the specific post where you got the quote from so that I could check what the context was. Otherwise, I can't remember what exactly was I saying.

Now, for your question,

そして背中には《黒いほう》ことエリュシデータが. 50層ボスのラストアタック・ボーナスですが、STRが足りなくて前回までは装備できなかったというウワサ

The first sentence is explaining that the "black one" on his back is named "Elucidator". The second sentence is saying that he got the sword as a Last Attack bonus from (a/the) 50th floor's boss, but he couldn't equip it until last time as his STR wasn't high enough... and the sentence ends with him saying that it was a rumour.

So, for the part that interests you, 50層ボス means "50th floor's boss". It doesn't say "the" (since Japanese doesn't have articles like English), nor does it emphasise "floor", but I believe it's safe to assume that he was referring to THE boss, since he would have indicated what specific type of boss it was if it wasn't a floor boss.