You know, because Dark Souls 3 can never be too difficult, right? Of course not, and this particular mod, named Enemy Onslaught, surprisingly turns the game into a chaotic brawl of sheer insanity.
So how does it work then? Well, basically every enemy in the game is duplicated, and that means every one, including bosses. Double the fun, right? Interestingly though, the mod also duplicates the spawning of friendly NPC summons, which restores some balance to proceedings.
Unfortunately though that's the only advantage you're getting, and indeed, some of the side effects of the mod are pretty insane (and hilarious), my favorite is that fact that, due to the way the mod works, the second spawned boss does not have the same event ID as it's original spawn, and thus can leave the boss arena just like any other enemy.
It's pretty much impossible to play beyond 3x enemies, and some of the bosses you're going to need help to defeat, but it does highlight one particular quirk of the game engine rarely seen, if so many enemies are already attacking you, others will give you some distance until less enemies are engaging you.
So if you're looking for some more Dark Souls 3 pain and anguish, you can download the mod here.