[chapter 1110 spoilers!]
chapter 1110 reveals to us the mythical zoan forms of all five elders- as some people theorized, they’re all youkai of various sorts.
saturn is a gyuuki or ushi-oni (牛鬼), a type of ox-demon with clawed spider legs said to spread illness and spit poison.
mars is an 以津真天/itsumade, a type of ‘monstrous bird’ said to repeat いつまでいつまで/itsumade, itsumade (‘until when? until when?) during times of plague in myths dating back to the kenmu period. its name is also pronounced itsumade, but spelled with four different kanji.
warcury is a 封豨/houki, a boar monster said to be prone to violent rampages, destroying livestock and fields and killing and eating people. it also has a very tough hide which regular weapons cannot penetrate.
nusjurou is a 馬骨/bakotsu, ‘horse bones/skeleton.’ on a quick look i couldn’t find a good source with much more information about this one, but this blog post, citing the edo-period youkai book tosa obake zoushi, refers to it as a spirit of a horse that burned to death.
and then jupeter is a アンドワーム/sandowaamu, ‘sandworm’, a youkai famously originating from frank herbert’s dune.











