The Tiyalashe plains are in the northeastern part of Ara'phis and into part of southern Narbuzad. This area was once home to normal-sized herd animals. These began to lose out late in the Horgon Era when an island called the Ark of Devgwer smashed into Ara'phis. This island, ripped unnaturally from Gorejun (c.f. Devgwer Rip), brought with it thousands of dinosaurs. The predatory ones wiped out the local population of smaller herd animals, being replaced by larger and tougher dinosaur herds. Tiyalashe became a haven for dinosaurs and naturally a very dangerous place to visit. Civlizations on its fringes build tall walls and only send out patrols or hunting parties into the area when mounted on tamed dinosaurs. Some groups use raptors as mounts though due to their high meat requirements and unpredictably, this is rare.
