Complex sentence: Olver, via the Horn, helps see off the remaining forces of the Shadow, while a wounded Aviendha is cornered by Graendal and under imminent threat of Compulsion, manages to reverse the Forsaken's weaves, inadvertently making Graendal her mind-controlled servant.
Split into simpler sentences: Olver, via the Horn, helps see off the remaining forces of the Shadow. Aviendha, wounded, cornered by Graendal and under imminent threat of Compulsion, manages to reverse the Forsaken's weaves, inadvertently making Graendal her mind-controlled servant.