Here is the full list of all 9 Ontotis achievements.
Collect all 20 journal entries.
Listen all 3 cassette recordings.
Find the Eresys tome.
Answer the phone of the past.
Trigger the echoes of the past scene.
Escape the haunting past and leave this nightmare behind.
Cross the veil and find peace in death.
Learn about John's life story.
Complete all the chores inside the house.