Verdall is sort of like an alter ego to Dylan's main character, Nydall. while Nydall is typically shy and meek, Verdall is more outgoing and tough.
here's a brief description Dylan wrote of them: "Verdall is a practical Yoshi who is friendly enough to pass for a normal person. Secretly, though, they’re always trying to find a way to make life better or easier in the location they are at (they will often times accidentally make things worse though). They will typically work themselves into exhaustion, and sleep for longer as a result."
they are also androgynous, preferring "they/them" pronouns, and actually has (though maybe a bit nsfw) both male and female parts