These WoW Classic realms shackle players with the same permadeath punishment offered in Diablo 4, which has led to some truly hellish deaths for its players. WoW Classic's an especially dangerous arena, though, thanks to its habit of huge aggro radiuses and punishing enemy placement. Because of this, it's pretty easy to find yourself ambushed by murlocs—and I can only imagine the corpse pile around Hogger.
While death is final, you can still futz around Azeroth as a ghost after shuffling off its mortal coil to handle stuff like passing on guild membership—or to just haunt your friend Dylan for breaking your polymorph in a dungeon "because it would be funny". Once you're done haunting Dylan, you can transfer your dead character to a non-hardcore Classic realm.
Battlegrounds are also disabled, presumably because no-one'll want to risk their hides in mass warfare. But, if you really want to live your life on the edge with a group of like-minded sickos, you can still arrange the quickest and bloodiest game of Warsong Gulch Azeroth has ever seen.
One command, /makgora (named after the orcish Mak'Gora, a challenge to single combat) allows you to duel other players with permadeath firmly on. That's one way to settle loot disputes, I guess. There's also a new tracking aura that'll display how many bouts of orcish roulette you've survived, which is an admittedly tempting bragging right.
To stop some of those ill-fated Diablo 4 runs from repeating themselves, Blizzard have put in a few safeguards. You can't kite enemies into capital cities anymore, and there's a reduced log-off timer to stop disconnects from spoiling runs—oh, and Paladins can't bubble hearth, which feels spiteful, but very funny. Other than that, there's nothing standing between you and an inglorious death at the hands of a pack of angry kobolds. You can read the full list of update notes for yourself.