I looked for it, and it's different. Here's the video I mentioned.
https://youtube.com/watch?v=xpH4bhYYFwISkip to 3:57 to get to the method.
In short. 24 d6, drop the 4 lowest, arrange into groups of 3 from lowest to highest. Assign those as you like.
might as well grab dungeon crawl classics and do a funnel. preferably with enough beer.
I can recommend Descent however. I've only played the Tabletop Simulator version, but it's so much a DnD like that I'm fairly sure you could homebrew a campaign with basically no issues. The only thing it lacks is social and utility skills.
the problem with descent (and I like descent) is that it doesn't really work properly either way. if you play it as the asymmetric pvp game it's supposed to be, there are too many edge cases and it's too snowballing, on top of needing someone who likes being the sole bad guy, does it well but without being a cunt about it.
dorn does a much better job with simpler rules. good luck getting a copy tho, it was niche even when it was still available (and no scan up on TTS). website seems to be dead as well, I might at least write all the texts down as some way to archive it...

tbh I can't even remember any "good" games with the same premise, not that were many to begin with.
if you play it as a "pve" game where the overlord behaves as the gamemaster providing the AI for the monsters, it will bore him to tears because that's all he will be doing. might as well grab a homebrew like redjak's and let him join as a player:
there are also some official coop variants, but since they were POD only probably impossible to get these days. otoh the app works well enough for what it's supposed to do and I got around by now using an app even if it's still clunky and redundant in some way (moving shit like the app tells me to I might as well play it fully digital, even on TTS it can be annoying). however it was among the first implementations being tacked on an existing game so it's excusable, journeys in middle earth incorporates the app much better imo (to the point I'm eager to keep playing it). and with valkyrie there are plenty of homebrews:
https://github.com/NPBruce/valkyrie/wiki/Valkyrie
oh and also check out
3e legends of the dark if you haven't, that shit is hilarious. interesting idea tho and you can atleast use the cardboard stuff heroquest style for something else.
or skip all that and pick up this:
HeroQuest love from what I've seen is a decent game that is unfairly deified by nostalgia + scarcity since it was out of print for a long time.
heroquest is the super nintendo mini for true nerds. all the kids who grew up and played it in the 90's are now old enough to have a massive nostalgia-boner for it (even more with nerd shit being popular), to the point they can't stop gushing about hasbro
fleecing them with the same nostalgia bringing it "back", and telling everyone what a great game it is without having played it in decades.
then they pay 100 bucks to put in on a shelf, or maybe play it once and suddenly remember it isn't as great as back then...
otoh it gave us this, so I can't dislike it too much: