Here is the full list of all 15 Eldritch achievements.
Perform the complete Ritual of Binding.
Perform the Ritual of Binding.
Finish the game in New Game+ mode.
Acquire the Soul of Cthulhu.
Escape the Mountains of Madness.
Acquire the Soul of Nyarlathotep.
Destroy a lizardman statue.
Acquire the Soul of Dagon.
Read the complete History of the Library.
Finish the game in under 10 minutes.
Finish the game without taking any damage.
Deposit 9,999 artifacts in the bank chest.
Make friends with a star-spawn.
Free 500 trapped souls from the Asylum.
Survive for 3 minutes after Azathoth appears.