@Revenant Wings  
Without the fissure on Riven, and the events that caused and followed its opening, we wouldn’t have Myst.

Twilight Sparkle: “I realized the moment I fell into the fissure that the book would not be destroyed as I had planned. It continued falling into that starry expanse, of which I had only a fleeting glimpse. I have tried to speculate where it might have landed, but I must admit such conjecture is futile; still, questions about whose hooves might one day hold my Myst book are unsettling to me. I know my apprehensions might never be allayed, and so I close, realizing that perhaps the ending has not yet been written.”

Ah, time for a nerd’s debate: canon side stories place this fissure on Riven, but this is part of the opening for Myst. Does the “riven” tag stay or go?