[EDIT: This is an old post, now. Going to try to revitalize the story, starting here]Hey all, sorry, real life ate my hands and screwed up my forward momentum with Vanod.
I think at this point it's best to let him walk into the cave and never come out.
I can do you all a solid, though, and let you know how I made this world. I guarantee you'll have more entertainment that way, and hopefully can hold Vanod in your hearts as a forbear to your naked volcano island adventurers.
To make a Monster Island map, Design a New World with Advanced Parameters.
Make a Medium, Large, etc size map (depending on standard number of monsters you want)
You can always edit the number of semi megabeasts, megabeasts, night creatures, and so on.
I highly suggest turning number of Bogeymen down to 0, as you'll most definitely NOT find someone to be your companion and will lose all adventurers to bogeyman swarms.
Here is secret #1 to the weirdass Monster Island world: in the advanced parameters, make sure to dial the Maximum Elevation down from 400, to a suitably low number. For instance, I tried out an elevation of 20 and got it to work perfectly.
Secret #2 is to turn minimum number of mountain peaks to 0, and turn minimum number of volcanoes to 1 (unless you want more, of course, but 1 is the magic number to get all of the horrible monsters on one tiny island). Not sure if this works on mountain peaks, but if it does, it may be more fun, as you could go underground if you lucked out with a cave that reached caverns.
Let the map run. You'll get a LOT of rejects, but just be patient. When it pops up that you can't spawn [specific parameter], press ALLOW ALL REJECTS (even if you get a Legends only world). It'll continue as normal, but you won't notice anything on your map till it starts giving you a history, as it doesn't place volcanoes till very late- sometimes it only shows ocean through the entire world gen, even though the volcano island is technically the centre of the cursor.
Accept the world, make a human outsider (or modded race of your choice), and enjoy. Please feel free to share in here, if I find the time I'd love to draw your adventures- or at least your adventurers- too. Sorry again for lack of Vanod, but maybe it's better if his adventures end on a mysterious cliffhanger anyway.
I did manage to sketch up one last picture of Vanod for you guys.

Perhaps this is him at the mouth of the cave, ready to face whatever creatures lay within. Though I know what's inside, I'll leave it up to everyone's imaginations.

If you dudes have questions at all please lemme know. I should be able to reply here and there, though art takes me a while right now.