Legolas was quite enough to help Aragorn pull Yavanna and Boromir away from the broken edge of the bridge, although he did keep a good arm around his beloved while pulling her to safety. They were immediately informed that they were being pursued by a Balrog, a demon of the ancient world, whose power was beyond any of them: A massive, forty-foot man-beast, with horns surrounded by flame! By Gandalf's order, Aragorn was forced to lead the group down the stairway, until they managed to get to the bridge which seemed have a gap in the middle of it. The Elf Prince decided to go first, so he could easily catch the others that followed after him; Gandalf went after him. 

Right after allowing the princess to follow after him, arrows were whizzing past them from a distance. The Goblins were, once again, trying to advance upon them. It only took a matter of seconds for the blonde elf to retaliate, before Saeril glided across with Kili in her arms.