Oathstones are runic marker stones, about 3’ in height and half as wide. They are set approximately a half-mile apart from one another, creating a large area around towns, villages, cities, and even along great roads. They serve as a ward against unnatural creatures entering civilized regions without warning. Typically, clerics devoted to civilization and protection will bless oathstones, but in particularly large or metropolitan regions, even those deities dedicated to Night with a vested interest in stability so that they may ply their trade unhindered (such as those of the Whore or the Tyrant) may dedicate resources to maintain oathstones. The divine power inherent in the stones keeps most mindless and weak unnatural creatures away from civilized regions and encourages more powerful or malevolent creatures to use proxies and servants when seeking to infiltrate civilized lands.
Beasts, plants, and other natural creatures (such as humanoids), may cross an area warded by such stones without notice. Abberations, extraplanar beings, and the undead experience discomfort and pain when crossing an area protected by oathstones. Additionally, the warding priests will experience a similar discomfort when powerful creatures enter a warded area. Such creatures make attack rolls and saving throws at a disadvantage after crossing the line of oathstones for 1d4 hours or until revitalized by a restoration spell (lesser or greater).