From recent work, it seems that you would have to fight to destroy a bridge, not to prevent its repair; if you have to do the latter, well, see the Dragonheart trilogy for what you might have to have at hand.
Overall, I would read 'Worlds Without End', as well as the short story where Harlequin is drunk and a cloaked figure (Yrsgrathe, I think, but I don't recall) comes to him and taunts him. Most lower Horrors want instant gratification; most higher Horrors weave deep- and long-range webs of intrigue, deceit, and mayhem to further their goals - which are, essentially, to achieve complete, total, and eternal dominance over the Name-Giver races.
So if you're looking at how to do this, think a blend of the long-term planning of the Immortal Elves and Great Dragons, and blend in the eagerness of humans and orks to seize an opportune moment.
Or, you know, just channel Captain Jack Sparrow.