Stonethorn is the star of the show, introducing two new dungeons called Stone Garden, located in the depths of Blackreach, and Castle Thorn, ruled over by Lady Thorn in Western Skyrim. You can actually take a 360 tour of Castle Thorn in a new tool released by the team on Facebook. Check it out here.
A host of new item sets are released as well. For example, Castle Thorn receives Talfyg’s Treachery (Light), Unleashed Terror (Medium), Crimson Twilight (Heavy), and Lady Thorn (Monster Mask). Stone Garden, meanwhile, receives Elemental Catalyst (Light), Kraglen’s Howl (Medium), Arkasis’s Genius (Heavy), and Stone Husk (Monster Mask).
A bunch of new achievements and titles, in addition to new dyes and collectibles, are also part of the PTS patch. The base game also receives several stability and performance improvements. New furnishing, outfit style cost reductions, and much more are touched on as well.
For a full list of the very extensive patch notes, check out the official forum post here.