Dungeon Crawl - Where adventurers go to die

I would argue it is pretty much the most important part of the genre though? Realm of the Mad God has permadeath and I think randomized maps but I certainly wouldn't call it a "multiplayer roguelike". Permadeath isn't the hallmark of a roguelike, just one aspect most share; Isaac just doesn't feel like the same kind of game as most that call themselves, or get called, roguelike.