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