Forest

In a sparse forest, the maximum distance at which a Perception check for detecting the nearby presence of others can succeed is 120 feet. In a medium forest, this distance is 90 feet, and in a dense forest it is 50 feet. The Narlmarches is medium forest on its outskirts (a hex contiguous to hills, plains or swamps) and dense forest in the interior.

Because any square with undergrowth provides concealment, it’s usually easy for a creature to use the Stealth skill in the forest. Logs and massive trees provide cover, which also makes hiding possible.

The background noise in the forest makes Perception checks that rely on sound more difficult, increasing the DC of the check by 2 per 10 feet, not 1.

Plains

In plains terrain, the maximum distance at which a Perception check for detecting the nearby presence of others can succeed is 1200 feet, although the specifics of the map might restrict line of sight. Cover and concealment are not uncommon, so a good place of refuge is often nearby, if not right at hand. The Kamelands are plains with high grass (with the same mechanical effect as undergrowth) that provides near-constant concealment for anyone who attempts a Stealth check.

Hills
In gentle hills, the maximum distance at which a Perception check for detecting the nearby presence of others can succeed is 120 feet. In rugged hills, this distance is 60 feet. The hills in the Greenbelt are generally gentle hills but the hill terrain approaching the Tors of Levenies are rugged.

Ridges or peaks afford cover and concealment to those on the other side.

Mountains
The maximum distance in mountain terrain at which a Perception check for detecting the nearby presence of others can succeed is 400 feet. Certain peaks and ridgelines afford much better vantage points, of course, and twisting valleys and canyons have much shorter spotting distances. As in hills terrain, a ridge or peak provides enough cover to hide from anyone below the high point.

It’s easier to hear faraway sounds in the mountains. The DC of Perception checks that rely on sound increase by 1 per 20 feet between listener and source, not per 10 feet.