A conclusion from an analysis of the lore on the subReddit by one member speculates that,
Overheard in Tamriel
The Nirnroot is another cousin of the Hist, like the Sleeping Tree and the Umbrielian Hist. It shows far too many signs of being related to not be related. It’s not nearly as smart/sentient as the Hist or even the Um-Hist, but it has the wherewithal to enter a state of dormancy when times get rough.
Zenimax Online Studios has posted a nice summary on Master Writs on their website.
Master Writs are mysterious, exclusive contracts for high-quality and very specific equipment, or very specific alchemical substances, enchantments, or provisions.
It is fun to learn by Alchemy by trial and error and hope whatever ever does not kills you makes you smarter. However, an Alchemical Potion Recipe book does reassure an aging mind of success and less of death.
Only the finest master crafters in Tamriel receive special master writ invitations from Rolis Hlaalu, the Mastercraft Mediator.
To become a recipient of these prestigious documents, crafters have to be certified, be recognized as a master in their profession (Level 50), mastered all of the proficiencies in those professions (Solvent Proficiency 8, Metalworking 10, Tailoring 10, Potency Improvement 10, Recipe Improvement 6, and/or Woodworking 10).
Once you successfully complete a master crafting writ, you will be rewarded with writ vouchers that can be used to purchase special recipes such as the target skeleton, legendary furniture for each profession, components of the Aetherial Ambroisa recipe, and more.
Tianlein has posted a great video on the basics of Furniture Crafting. The pace is good and content is clearly explained. She includes a nice graphic of where the furniture materials are harvested and what the types of blueprints, diagrams, etc. for each crafting profession are. Looking for a quick primer? This one is worth your time. Duration: < 4 minutes.
Codeman1976 has shared a very useful crafting tool on the official forums that generates a list of all the items needed to craft various gear sets. It was created for his guild Shadowscales of Black Marsh.
There are drop down boxes to build the crafting order and generates the list as you progress through each of the boxes. You can use the generated text to cut and paste into the game UI to mail or whisper the needed components to your client.
