"The claws of a hagraven are best obtained in shops; it is inadvisable to suggest one collects them oneself. These creatures have traded in their humanity for access to powerful magics, and the transformations they undergo infuse their entire beings with some element of that power. Ingesting the powdered claws makes one more resistant to magic, but an especially curious property of the claws is revealed when mixed with snowberries (often found in Skyrim's higher elevations). I found myself capable of comprehending enchantments I had believed mystifying after ingesting the mixture, and have passed this knowledge on to several court wizards who were grateful for the knowledge." - Agneta Falia in the Herbalist's Guide to Skyrim.
Harrada comes from the Harrada Root plant, which is native to Mehrunes Dagon's realm of Oblivion, the Deadlands. Normally Harrada Root plants are not found in Tamriel, however they take root outside of certain Oblivion Gates that lead to the Deadlands.
Heather is a low evergreen shrub native to the Ascadian Isles region of Vvardenfell. It's known for its small, pinkish-purple flowers and modest magical properties.
Hunger Tongues are harvested from Hungers, a ferocious Daedra. The tongues can be used by alchemists as an ingredient in potions to cure diseases and aid those who are afflicted by poison.[1][2]