if you play games, you can see skill names or items like, Blade of the Ruined King or something like that. is it ok if I use lowercase instead of capital letter? doesn't it seem awkward to native english speaker? - like, blade of the ruined king.
Grammatically, you should always capitalize a proper noun in English. Since your game items are presumably unique, their names should also be capitalized. Here is a reference for identifying proper nouns. If you plan to make a published work, like a review of this game, you should capitalize the item names.
That being said, online games tend to have a very casual atmosphere, and it's very rare for the players to care about each other's grammar at all during play. In fact, even abbreviations, like (all-lowercase) "bork" for "Blade of the Ruined King" are thrown around all the time. So don't worry about it in-game. Source: I also play League.
