Classic Hardcore realms are opening at 3:00 PM PDT on August 24. 

There will be 2 Hardcore Realms at launch called Defias Pillager and Skull Rock. Here are the update notes for Patch 1.14.4 with all the fixes.

(Source)

Hardcore Realms

New Classic Era Hardcore realms will open at 3:00 p.m. PDT on August 24.

When a player-character dies on a Hardcore realm, they cannot resurrect or be resurrected by any other spell or ability. After death, the player-character continues to exist in the game world as a ghost to facilitate communication with in-game friends and resolve logistical matters. The character is not necessarily lost, however. After dying on a Hardcore realm, players will be able to choose to utilize the Free Character Move service and move their dead character to a non-Hardcore Classic Era realm. Once the move is complete to the non-hardcore realm, that character may resurrect as normal.

On Hardcore realms, players are not automatically flagged for PvP upon attacking another player. To flag yourself for PvP, you must type the command /pvp.  You won’t be able to take hostile actions against a flagged enemy player unless you flag yourself deliberately. PvP battlegrounds are completely disabled, as are all PvP Battlemasters. You may enter premade Wargames, but you may not gain honor or PvP reputations from Wargames.  Various quests and objectives that cause players to become PvP flagged, such as the quest “The Attack” and “The Missing Diplomat”, do not cause players to become flagged for PvP.

All dungeons have at least a 24-hour lockout timer for players below level 60. Furthermore, level 60 players may never enter lower-level dungeons with players below level 60 for any reason. Additionally, group experience restrictions are in place, as they were on Season of Mastery realms. Players who are significantly higher level than the creatures in a given dungeon will cause those creatures to grant trivial experience to the other members of the group.

The 16 debuff limit and 32 buff limits have been removed on Hardcore realms. Paladins will not be able to use their Hearthstone while under the effects of Blessing of Protection, Divine Protection, or Divine Shield on Hardcore realms.

A new feature is available on Hardcore realms: Duel to the Death. To issue a Duel to the Death, right-click the target’s portrait and request a Duel to the Death from the context menu. A Duel to the Death can also be triggered by selecting the target and typing /makgora in your chat window. Before commencing combat, both parties must read and acknowledge a warning message and type “I Agree” to begin. Death in a Duel to the Death is permanent, just like any other death on Hardcore realms. The number of kills you receive in Duels to the Death are tracked and rewarded with a special cosmetic buff on your character called “String of Ears”. Each time you win a Duel to the Death, you will receive a “trophy,” and the stack count on this buff will increase by 1. Anyone who clicks on your character will be able to see what a frightful combatant you are by the number of Ears you’ve collected. You cannot earn the String of Ears buff before level 10, and you cannot earn the buff if you and your opponent are too many levels apart.

Hardcore realms will have all the original WoW Content phases unlocked and available right at launch.

Classic Era PvP Ranking Update

On Classic Era realms, the PvP Ranking system has been revamped. In the reworked system, Ranking Points have been eliminated, Honor is visible immediately after each Honor Kill (or Dishonorable Kill), and de-ranking is no longer a factor, making the system less punishing if you take breaks from ranking. Most importantly, your Rank is no longer determined by a comparison with other players, and the amount your rank increases each week during the weekly reset is solely determined by your PvP efforts in a given week.

Maximum honor gains for the week are currently set to 500,000 Honor per week. If you earn 500,000 Honor in a given week, you will reach the maximum progress possible in a single week. Earning over 500,000 Honor in a given week will confer no other bonus nor cause you to rank faster.

Fixes

Fixed an issue that allowed certain raid buff items from the Season of Mastery version of Naxxramas to be used in Classic Era realms.

Fixed an issue that could cause players to disconnect from the game when pressing the space bar to swim upwards while underwater.

Fixed various issues with Vanish and Feign Death that could be used to flag nearby players for PvP.

Fixed various issues that could cause enemy creatures to fall through the world when pathing through water.

Fixed an issue with the Summon Incubus ability costing less mana than Summon Succubus.