[SPOILER] Finished finally but a question remained

[Sarcelle]

Spoiler below!

I'm pretty certain that it's you. Mandus is crazy. He mentions that when he returned from Mexico he split into two. One of them built the machine, and the other lay dormant, which you play as. In the beginning Mandus is trying to hold onto his sanity and thus imagines that he's talking on the phone. Which sorta explains why they always ring just as you go by. But by the end he drops the pretense. It's a conversation happening within his own head. I think.