Here is the full list of all 22 Thorne - there are Death Merchants achievements.
Speak with the Death Merchant
Slay the Abyss Mermaid
Find out about Eldyn's suicide
Take the Lycan's contract
Karma is a...
Convince Skillet into releasing you
Take the blame for Idegert's murder
Find the Fallen King's Crown at Fire Isle
Slay the Wyverns at the Lighthouse
Bring Olav the antidote
Speak to Faida at Ocean View
Defeat Ray at Gang's Hideout
Find the accessory near Simeone's Cave
Destroy the nests at the Goblin Cave
Defeat the Revenant
Save Matthias from Ray's Gang
Speak to Layla at Hollow Lake's bridge
Face the Lycan at Hollow Lake
Meet McArthur at the Estate
Find the Rowens near McArthur State
Speak with Layla at Hollow Lake
Defeat Ray at Dead End