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