The Diablo series was the name of a famous popular series that combined aspects of rougelikes with the ever popular action rpg, with realtime combat. Traditional roguelikes are turn based affairs, hard to complete with many many deaths. Action games are just mow down a lot of monsters. What the diablo series did was take the random loot aspect, and combined it with the random dungeons aspect, while still keeping the traditional mow down hordes of monsters game mechanic of action rpgs.
I don't think we have ever had anything quite like that in free software, sure we have flare, but I'm not sure how random that is (I don't recall it being very random when I played it last) and we have all the traditional hardcore roguelikes. I'm never sure why we didn't combine them to get some kind of breakaway ever popular success project that would be diablo without everything bad about it (I mean all the problems with it being inherently proprietary)
Oh wait, we did, it was called Crossfire, but it kept too many of the mechanics from old school roguelikes. It kept the death penalty, but it toned it down. Also, I don't think the dungeons in diablo were all that random, honestly the ones in runescape are more random with the dungeoneering skill.