It is The World, yeah. Or an evolved form thereof. Green baby is how Dio's getting to Heaven. XD;;; I hadn't thought at all of the Joestar "minor technique" vine property but you're right, that would make sense as to why it's a plant.

(Well, that and there's a metric fuckton of Osirian imagery that's not even explained, just dropped there for the alert reader to gawk at. XD The code words that Pucci spouts... I should just continue with the summary.)

Dio is a good deal cooler retroactively in part 6, yeah. XD However if I'd ficced him after parts 1-3 I'd probably have written him much like this regardless. Not sure what this says for me, other than that I share Araki's thing for Italian Renaissance art that is. XD