Eren is a psychomancer. He can listen to the mechanical workings of a ship and hear the voices of deceased people who touched the ship or its parts last. The voices tell him how to solve mechanical problems, and in exchange they simply wish to be heard so that someone will remember their stories, the stories of the current ship and all others where the parts may have been used before, or the places where the ship has docked that no longer exist.
Eren has a particular dislike of rust, which he feels is like cancer. In his opinion, "rust creeps" and distorts the voices so they sound like whines or shrieky, tattered howls. This opinion also means Eren does not like working on Minmatar ships, owing to the high level of rust found in them. Eren also dislikes working on colonies because there are "too many buried there".
When Eren becomes an old man he can no longer hear the voices. Instead, he hears something beyond them, something which he describes as never falling quiet.