Route 10 is a route between Geosenge Town and Cyllage City. It is lined with mysterious stones (based on the Carnac stones), which are actually the graves of Pokémon who were sacrificed 3,000 years ago in order for their life forces to energize the ultimate weapon that was used by AZ to end the war. The stones, as noted by researchers such as Colress, usually put out energy. However, when the ultimate weapon is fully activated, that reverses and they begin to absorb energy from Pokémon.
While the ultimate weapon is present in Geosenge Town, Route 10 is completely closed to access. One Team Flare member blocking the area says that the player should not be exposed to the sights taking place there, presumably with the stones in the area. After the ultimate weapon is destroyed, it is revealed that Tierno and others were fighting Team Flare in the area.
Route 10 first appeared in PS586. After the initial activation of the ultimate weapon had failed to take any lives thanks to X and his friends, Xerosic discovered that the stones lining the area were actually an ancient form of the Absorber used by AZ when he first used the ultimate weapon. With the other Absorber destroyed when Xerneas awakened from its dormant tree form, Xerosic decided to use the stones as a replacement to refuel the ultimate weapon with Pokémon life energy.
In PS589, a group of Team Flare Grunts lined up the stones with Pokémon captured from Pokémon Village. Before they could finish their job of absorbing the life energy of the captive Pokémon, however, they were attacked by Viola, Alexa, Clemont, Bonnie, and Yvette, who had learned of Team Flare's plans and arrived to free the Pokémon they had captured and destroy the stones to prevent the ultimate weapon from ever being used again. With the other Gym Leaders taking down their reinforcement forces, the Team Flare members on Route 10 were soon defeated, despite the support of Malva's Delphox.
A Backpacker here mentions Colress once telling him about the mysterious energy emitted by the stones on this route.
After being defeated, Psychic Robert says that the player's Pokémon's "power levels" are "over 9,000 for sure," making a reference to the memetic phrase from the Dragon Ball Z anime series.