We previously datamined new Dreadlord's Regalia armor sets but cosmetic items to acquire these transmogs have finally hit the 10.2.5 PTR. It's still currently unknown how we'll obtain these new armor sets, but we do know these sets will be account-wide.
Will we see the Dreadlords return as part of the Reclaiming Gilneas story campaign coming in 10.2.5? They do love their gothic architecture after all.
The Dreadlords or Nathrezim returned to the Shadowlands during the anima drought as servants of Sire Denathrius and the Jailer. However, with the Jailer's defeat, the Nathrezim now only answer to Denathrius, yet the current whereabouts of Remornia, Denathrius, and the Dreadlords remains unknown.