Just a different kind of human like Moriah or Oars
A regular animal like Bepo
An animal who eat a new Hito Hito no Mi model
A Kaiju (i.e. Godzilla)
A Vampire, Mummy or other folkloric being
This is not my theory, but someone on the predictions thread suggested Kaidou might be a creature of Vegapunk
It would have be good if I had added dragon or machine to the pool.
I am going to go out on a limb and say he is either a Talking animal or a animal that ate a type of hito hito no mi. That or a human that ate some kind of badass Zoan like a mythical or ancient Zoan. I thought maybe a Neco Neco No Mi model Lion because we consider Lions to be the king of the jungle and it would kinda go with his king of beasts title. Though we already got shiki the golden lion and that lion turtle guy. What would be crazy is if Kaido is a giant or very large human who ate the Neco Neco No Mi model Lion. could you imagine how amazing it would look when a Kaido in full animal form appears in front of the SH and Heart pirate alliance. They would be stunned seeing a massive menacing Lion towering in front of them from some elevated position.
Dragon, based on Kinemon's reactions so far...
Allot of people think Dragon has dragon devil fruit so I am sure they would be against Kaidou having a dragon devil fruit, though I believe dragon is wind logia since it fits his whole winds of change persona so I guess Kaidou could be a dragon.
no mythical zoan option?
my friend suggested a theory about Kaido being mythical zoan user model Typhon, "The father of all monsters" of Greek mythology. Think that would fit his "100 beast" epithet perfectly.
Definitely a dragon.
There's been talks about Dragons since the beginning of the arc, and Kinemon hates dragons, etc, etc.
It's pretty clear that Kaido is a dragon.
Ceasar was creating artificial devil fruits that could mimick the Dragon fruit (Momo ate one of those artificial fruits).
The dragon idea does have traction.
I imagine Kaido is assembling a Smile army to contend Blackbeard, which makes me wonder about him even more... I like the Typhoon concept, but it's a hard design to imagine. Just because he was referred to as the most powerful creature doesn't mean he wasn't originally human though. He could just have a form that leaves that much more of an impression. If he requires transformation to make any significant action I would take note of that over the original man.
I want Kaido to be the Florian Triangle monster.