Solstheim – The Lost Levels is an add-on for the Dragonborn DLC that adds 5 caves, 8 plants, and 1 book. The content is based on The Elder Scrolls III: Morrowind and its expansion, Bloodmoon.
The caves are dungeons that were featured in Bloodmoon, but aren’t present in Dragonborn. They’ve been spread out across Solstheim, generally near their original position.
The caves are:

• Skygge
  
• Fjell
  
• Gronn
  
• Solvjord
  
• Rimhull

The new plants are mostly native to Morrowind, but some plants indigenous to Solstheim as it is portrayed in Bloodmoon are also included. They’ve been added to leveled lists and placed on the island, replacing the flora that you already know from Skyrim.
The plants are:

• Belladonna
  
• Wolfsbane
  
• Fire Fern
  
• Marshmerrow
  
• Luminous Russula
  
• Violet Coprinus
  
• Bungler’s Bane
  
• Hypha Facia

A brief history
In the distant past, a modder by the name of Ionisthebear worked on a Skyrim mod known as http://solstheim4e.blogspot.co.uk/. When it was revealed that there would be a DLC set on Solstheim, he abandoned the project. He had already completed the exterior world and a number of dungeons. He repurposed the custom assets for http://www.darkcreations.org/forums/forum/357-northpoint/ and the landscape for http://www.darkcreations.org/forums/topic/3444-wip-hircines-hunting-grounds/, but the finished interiors were sitting idly by, so Ionis gave me permission to implement them as a Dragonborn add-on.


http://www.darkcreations.org/forums/files/file/622-solstheim-the-lost-levels/