A new Neverwinter developer blog has shed some light on the Infernal Citadel Dungeon.
To reach it, you’ll go to one of the floating citadels above Avernus. You’ll have to break the chains, literally, and help out the cursed Vallenhas family. The dungeons are fraught with demons, tricks, and traps.
But even beyond these, there’s something called a Hellfire engine,
“Even if players survive all of the deadly critters, traps, chaos, and fire, they will be forced to face off with the massive Hellfire engine up close in the caged death arena the devils use to entertain themselves with the poor unfortunate souls they capture. But don’t worry, you won’t be intimidated by the skeletons of the previous arena victims, as they’ve all burned up in the magma bubbling just below the grated floor.”
The images and screenshots of the dungeon look really cool, which you can check out here.