Vigil Games further detailed the DLC today, which features a new swampy area called Shadow Lands. It includes two new dungeons, along with new enemies and unique loot. Vigil claims Abyssal Forge features "the hardest enemies and puzzles yet."
It'll also spotlight the meaty-looking dude in the above picture. He's an outcast known as the Mad Smith who's been wasting his years away by building an army, probably with that giant thingamabob he's holding. We expect he'll find another use for it when you meet him in Shadow Lands.