Following the Great Quake that was unleashed by the emergence of Dominus and The Swarm, various faults and sinkholes that quickly led to the discovery of a vast network of tunnels that covered the whole country. These tunnels are a mixture of man-made, Sandworm made, and "other" made. Several of the hundreds of tunnels seem to have been, or are still currently, used by the human trafficking network in Wind Country to transport their "merchandise". Due to that, there is an active underground train system and mine cart paths to expedite travel to all reaches of the country... if you can negotiate your way onboard. This nefarious system is the actual "highway" while others choose to travel "off-road" in the various other tunnels, at their own peril. "Off-road" paths treasure, creatures, and civilizations either forgotten or never discovered before!