1: Existing here would instantaneously kill your character. With a big explosion. Massive one. 

2: Existing here would likely kill your character. Probably because shadow-oxygen isn't a thing.

3: Existing here would probably kill your character. Because breathing in would probably prolapse your lungs or something else zany or random.

Ah, there lies another issue. How would your character hold knowledge that they could not survive going to these places, even less likely is knowledge of these characters who are asshats?