sentences:  Eventually, Clavain and Voi depart and fly down towards the Great Wall of Mars, which turns out to be a massive construction that completely envelops part of the planet's surface (enough to cover a city) and the atmosphere above it.As they descend, they are attacked by robotic "worms"- war machines from the previous war with the Conjoiners.Clavain destroys the first worm, but more arrive and kill Voi.