Dark Sun Terrain: Forest

Temperate Forest in Heidelberg, Germany

Forests on Athas are living barriers that likely shelter venomous creatures looking for their next meal. Trees provide respite from the sun, but also make it difficult to spot your enemies. Of course, the strange trees and plants may try to kill you before any enemy on two legs. Rain is most common in the forests of the Tablelands and it is unlikely characters come prepared for all of that moisture. Thri-kreen chitin may rot if exposed to the forest's wetness for too long and so can leather armor and hemp rope.
There are many different types of forest and they do not necessarily look alike. This is usually based on the amount of rain fall that pours down from the sky. No place in the Tablelands get as much water as the forests. There are two types of forests on Athas, temperate forests and tropical forests.
Temperate forests tend to have trees with dense, strong wood, like agafari. The undergrowth consists of ferns, fungi, moss, and shrubs. Temperate forests are darkened by thick canopies that shade the forest floor and fog is common in the morning and evenings. The Crescent Forest and a majority of the Forest Ridge are temperate forests.
Tropical forests get more rain than temperate forests. These forests are thick with vegetation and mud. The canopy tends to be extremely thick, darkening the forest floor considerably. All of the undergrowth in temperate forests are present in tropical forests, but in greater numbers. In addition, there are flowering plants and vines. It is not uncommon for trees in tropical forests to grow to incredible heights, but the trees tend to be thinner than in temperate forests. Only the deepest parts of the Forest Ridge are tropical forests.
It's important to note that Athasians would not use the terms temperate and tropical.

Tropical Forest (aka Jungle) in Philippines

A dizzying number of creatures call forests their home, as well as numerous deadly plants. A forest traveler should be extremely cautious when traversing through the trees and shrubs, as the creatures they encounter make their homes in these plants. High in a tree, or low among its roots may be the home of a deadly agony beetle or venomous snake. Athasians should not feel safe inside of a forest, for death lurks everywhere.
The terrifying athasian sloth makes its home in the forest, as do kirre and other great cats. Agony beetles and even horrid nightmare beasts live in forests. If the creatures don't kill you, the plants just might. Brambleweed grows in great abundance in the forest, as do poisonweed, bloodvine, blossomkiller, and mantrap. It is advisable to hire a guide to help identify and avoid the unpleasant flora.
Traveling through a temperate forest is difficult and a tropical forest is extremely difficult. Often a path must be cut through the trees with swords and axes. The ground is rarely level or dry, so footing can be hazardous. In addition, forests are rarely quiet, with animal calls creating a sonorous roar all around them. If the forest ever falls silent, it is an ominous warning.
It is easy to get lost in the forest, if not following an established trail. Destinations cannot be seen and obstacles are pervasive. Navigating around rocks, trees, and large patches of brambleweed can easily confuse a traveler. Sunlight is obscured, which creates dark shadows that reduce the ability to see very far. Shadows play with the mind, but may also conceal an enemy. Kanks, inix, and mekillots do not navigate well in the forest. Erdlands and crodlu are better mount options.
Thankfully water is not difficult to come by and nether is food, if you know what is good to eat and what is poison. There are also enough animals in the forest that hunting is easier than in other areas of the Tablelands. Food tends to rot a lot faster in the forest, due to the moisture, so storing food is more difficult than normal.

Official Rules: All creatures move at a third of their movement rate through a temperate forest and a sixth through tropical forest.

House Rules: Kank and inix are reduced to a quarter of their movement speed in temperate forests and an eighth in tropical forests. Mekillots have their movement speed reduced to one in temperate forests, as they must constantly smash through trees that are in their way. Mekillots may not move through tropical forests with any amount of haste, their movement speed is reduced to one every three rounds. When using the water find or hunting proficiency, the user is granted a +4 terrain bonus. If characters spend the entire day in a forest, their water requirement is reduced by a third.

Temperate Forest in Yakushima, Japan