Thanks to the help of a mega weeb friend of mine we've put together that "Hakuba" and "Kokuba" are likely a combination of "haku" and "koku", 白 (white, colour) and 黒 (black, colour) respectively and 馬 (horse) which can be read as "ba". So my best educated guess is they are white and black horses respectively.

How they will fuse with Calyrex is anyone's guess. It could just ride them as a steed, but seeing as the trope with the new legends so far has been Chinese mythology, I don't think it's a stretch to imagine they will combine into some form of "qilin", a mythical creature which have been described as deer x dragon x horse hybrids.

Thoughts on typings? Themes? Abilities? Anything else? Discuss.