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