"Thestrals, as I know can be seen by those who had seen death through their families or loved ones. I also think, but not really sure, when you had a near-death experience yourself, you'd also see thestrals," Erin raised her hand as her CoMC professor asked about the invisible creature.

Just the idea of thestrals was hard enough to contain. Erin did experience losing a loved one by her mother, and seeing one thestral would just remind her of the piercing memory. It wasn't like, you'll just passed by the memory. It stays there until you're ready to move on.