Starchampion

I believe that the Shadesmar is connected, or focused, at the pool where the Elantrians went to die. It would explain why it's dangerous to travel through the Shadesmar on Sel, as the only one who we know of who hasn't died there was Raoden. We know he's strong-willed/stubborn enough to fight against it, and retain his sense of self. And maybe the entrance to Shadesmar is different considering the location you enter? Like how Shallan had to reveal a secret, perhaps someone has to have a strong sense of purpose on Sel?

My theory is a little simpler (if you can get 'simple' in the Cosmere.) I believe that the Shadesmar is connected, or focused, at the pool where the Elantrians went to die. It would explain why it's dangerous to travel through the Shadesmar on Sel, as the only one who we know of who hasn't died there was Raoden. We know he's strong-willed/stubborn enough to fight against it, and retain his sense of self.