Thank you for your input, I really think this thread helped me develop a lot more ideas than I originally had for how the MC might end up internalizing their own immortality.
I’d imagine just how their immortality is framed is dependent on the species the player selects in part. Because one of the species you can start out as leaves you extremely aware that your immortality is not invulnerability. The existence of an ‘Achilles’ Heel’ to an immortal might fit well with those who were human and ended up in that state as the result of a gift/curse.