(Or more apptly Something is Wrong with Coràzon)
Here I have complied my variety of reasons as to why I think Coràzon could be an undead of some variety and is just straight up hiding it from the rest of the party...
1.) Suzette: During Dob's reunion with Suzette, she says some worrying things about Coràzon:
"Just, be wary of the pirate. Just between you and me I think he's taken a bit more than a few knocks and bruises, if you catch my meaning." and finishing up the conversation with "I think he's... yeah..."
Implying that Suzette thinks Coràzon is... something? And Suzette is a biologist of some description, so if there is something wrong with Coràzon she would pick up on it...
2.) Coràzon Cursed Status: Coràzon is very vague with why the curse came about and his role in it. In Spot of Bother, he says that he isn't cursed (not explaining how he avoided this fate when the rest of his crew couldn't). Though he will occasionally make a light refrence or two to the possibility. Such as jokingly saying "Yeah we're all cursed mate, get on with it," in Mind Your Manors.
So Coràzon is obviously hiding something from the rest of the Oxventurers about his relationship to the curse. What that is, we can't be exactly sure.
Misc. Theory Fodder: (aka circumstantial evidence that could relate to Undead Coràzon)
- Coràzon seems to know more about Egbert's Paladin abilities then he does, specifically in Elf Hazard in which he is basically begging Egbert to use Divine Smite on Banshee (an undead, which is weak to radiant damage)
- Additionally, Egbert is always the one Coràzon is pushing into dangerous situations (or talking about eating his flesh). Almost like he sees Egbert as a bit of a threat (considering he's a paladin, one of the parties main suppliers of radiant damage along with the possibility of him having the spell detect evil and good, a spell that can detect undead within 30ft, it would make sense Coràzon would think that way if he way hiding the fact he is not quite alive).
- Coràzon getting into the Necropolis on Sea Manor through the weird cat-flap in a way that is described to be upsetting, ("To be honest, all of you except for Prudence feel a bit sick. You didn't really think that this dashing young pirate could do anything quite so horrifying. You didn't think any human do anything quite so horrifying and still live..." - Johnny, Mind Your Manors)
- We are yet to see (to my knowledge) Coràzon take any life threatening damage (unlike the rest of the group who have been burned, disembowelled, poisoned, have their arm almost taken off, etc.)
- Coràzon taking 3 necrotic damage for bee puns, which he is not allowed to uncanny dodge (Bone 2 Pick)
-Also Coràzon seems to be constantly surrounded by undead (his old crew and his ghost pirate grandfather plus the skeleton army) and is generally a bit too chill about it
Anyway I think it would be a fun reveal!