"All of creation cares not whether you live or die."
The Soul Bridge is a path from another realm, invisible to eyes of living creatures. To reach the Iron Canopy and confront Silitha, War will need to use the bridge that links the Ashlands with Silitha's Lair. In order to do that, War uses Ruin to cross it, since the red horse has the power to awake this ancient bridge.
The Soul Bridge that links the Ashlands with the Iron Canopy is the only one found in the game.