Starting from https://glowfic.com/replies/1922141#reply-1922141

If it's a manipulation with weird compulsions and/or illusions, or just a nightmare, that's not reality.

EDIT: Someone suggested this might be a trick, where the initial communication isn't Altarrin. That wouldn't count, if that's true it's still reality. Unless, of course, there's other mindfuckery also taking place that is substantial enough that it would qualify on its own.