Anchor Stone

Source: Paizo Blog

This strange stone has a debilitating gravitational effect on those who do not traverse over it quickly. Each time a creature starts its turn on an area of anchor stone, it must succeed at a DC 12 Fortitude saving throw. Any creature that fails can only take a 5-foot step on its turn. Any creature that succeeds at the saving throw must move at half speed on its turn.

To take the effects of anchor stone, a creature must be standing on or touching the stone. Anchor stone has no effect on those who fly over it or otherwise do not have physical contact with the stone.

Some areas of anchor stone are more powerful than others, having a DC of 15, 20, or even higher.