Not long after the release of the rest of Phase 3 in WoW Classic's roadmap, which notably included Blackwing Lair, Blizzard announced the following: Arathi Basin will be available from March 10, 2020, while Zul'Gurub and the Dragons of Nightmare (Emeriss, Lethon, Taerar, and Ysondre) will appear in the game from April 16th 2020.
Arathi Basin
Arathi Basin is the last Battleground to be released in WoW Classic. It is a 15v15 capture point arena that can be accessed from Level 20. Arathi Basin pits The League of Arathor (Alliance) against The Defilers (Horde) in a battle over resources in this bountiful valley; you actions will decide who gets to reap the rewards from this Battleground!
Arathi Basin will be available from March 10.
Zul'Gurub
Originally released in Patch 1.7: Rise of the Blood God, Zul'Gurub is the ancestral home of the Gurbuashi trolls in Stranglethorn Vale. Unlike other raids in WoW Classic, Zul'Gurub is a 20-man encoutner and rewards players with items between Molten Core's Tier 1 and Blackwing Lair's Tier 2.
The assault on Hakkar the Soulflayer's lair begins on April 16, 2020 at 18:00 EST.
Tier 1.5 sets
With Zul'Gurub being added to the game, 9 new class sets will now be available. These Zul'Gurub Sets are commonly known as "T1.5" and are best known for catering to some overlooked and underplayed specs. They're also designed for PvP, making them well worth your while!
Here is our complete list of each class's T1.5 set:
The Nightmare Dragons
Known for their ferocity, this Green Dragon quartet offer max level players new items and extraordinary challenges. All four of these dragons were once guardians of portals to Emerald Dream, but have now succumbed to the Emerald Nightmare and now set out to bring their nightmarish terror to Azeroth's denizens.
Emeriss, Lethon, Ysondre, and Taerar will awaken on April 16th at 18:00 EDT.