The phrase 'black fire' would be translated as é»’ã„ç« (kuroi hi) in Japanese.
Kuroneko.
Kuroi sasori.
Kurotsuki
Kuroi Ame
kuroi inu
Kuro Kaze
Kurogokegumo.
kuro to shiro
Kuroi ie/uchi.
'Black thunder' would be 黒い雷 (kuroi kaminari) in Japanese.
There are no plurals in Japanese. 黒い竜 = kuroi ryuu, or lit. black dragon. Hope this helps~
Kuroi neko.