Fact
Per Icy Veins' account of the Oct 8 WoW: Forever podcast: Blackmaw Hold's entrance is the large brick gate in Azshara that Vanilla never used; it is the stronghold of a corrupted furbolg tribe dealing with demons, separate from Felwood's Timbermaw; a high-level dungeon with a tight level range, mostly run at 60 but enterable a little earlier, with quests. The encounter designers say it is not a mega-dungeon and should be finished in one long session, though probably a bit bigger than Blackrock Depths. No bosses named. Update (2026-10-11): Warcraft Tavern's account of the same podcast (at 39:07) quotes the developers on a 'larger footprint than Blackrock Depths' with a 'non-linear layout', plenty of verticality and many secrets, and says the dungeon will not be available during the beta.