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