The Poison Hills are the last ground Gorath truly holds before the Moon Wilds, and they earn the name. The soil grows things that kill. Sap-weeping vines whose touch raises welts, fungal blooms that fog a hollow with spores no lungs survive, fruit that looks like mercy to a thirsty man and stops his heart by morning. The animals match the plants. Everything here that crawls, bites, or stings carries something, and the things that eat the poisoners are worse than what they eat. A traveler who does not know the hills does not get a second mistake.
The country is a threshold. East lie the cleared Jungles of Titania and the heart of the empire; west, past the hills and across the Myublin River, the Moon Wilds begin and Gorathi authority ends. Drauso's legions staged through the Poison Hills on their way into the Wilds, and the broken remnants came back through them too. For most of the empire the hills are simply the edge of the map worth caring about, the place where settled Gorath thins into the country it cannot keep.
For the alchemists they are a harvest. The same toxins that make the hills lethal make them valuable, and Gorath's poisoners, apothecaries, and a quieter trade in worse things come to gather what grows here. A pouch of the right spores is worth more than a season's wage, which is why people keep dying for them. The boldest of the trade work fresh Vexling ichor, hauled back across the Myublin in the hour before it turns inert, and try to fix its corrosive bite into something they can sell. Those who survive the attempt agree it is not worth it. Those who do not are how the rest learned. The hills supply the empire's venoms and the markets of Azantir take them, and the body count is built into the price.