Here is the full list of all 20 Argonus and the Gods of Stone achievements.
Read all journal entries.
Complete all Achievements.
Set free the souls of all the Argonauts.
Set free the souls of all the isle's inhabitants.
Obtain every takable object on the isle.
Find all the broken pieces of wrecked ships.
Unearth a certain ancient skull.
Light all sconces and braziers.
Teleport to and from every temple on the isle.
Talk to every god on the isle.
Learn to use a forge.
Steal two things from their owner.
Talk to five gods.
Talk to four gods.
Ride a stallion three times.
Raise the dead.
Talk to three gods.
Find and place all the mosaic pieces.
Talk to two gods.
Talk to one god.