The +1 on melee attacks if you are on higher ground than your target
Walls with Arrow Slits: Walls with arrow slits can be made of any durable material but are most commonly masonry, hewn stone, or wood. Such a wall allows defenders to fire arrows or crossbow bolts at intruders from behind the safety of the wall. Archers behind arrow slits have improved cover that gives them a +8 bonus to Armor Class, a +4 bonus on Reflex saves, and the benefits of the improved evasion class feature.
Uneven Flagstone: Over time, some floors can become so uneven that a DC 10 Acrobatics check is required to run or charge across the surface. Failure means the character can't move that round. Floors as treacherous as this should be the exception, not the rule.
Hewn Stone Floors: Rough and uneven, hewn floors are usually covered with loose stones, gravel, dirt, or other debris. A DC 10 Acrobatics check is required to run or charge across such a floor. Failure means the character can still act, but can't run or charge in this round.
Light Rubble: Small chunks of debris litter the ground. Light rubble adds 2 to the DC of Acrobatics checks.
Dense Rubble: The ground is covered with debris of all sizes. It costs 2 squares of movement to enter a square with dense rubble. Dense rubble adds 5 to the DC of Acrobatics checks, and it adds 2 to the DC of Stealth checks.
Natural Stone Floors: The floor of a natural cave is as uneven as the walls. Caves rarely have flat surfaces of any great size. Rather, their floors have many levels. Some adjacent floor surfaces might vary in elevation by only a foot, so that moving from one to the other is no more difficult than negotiating a stair step, but in other places the floor might suddenly drop off or rise up several feet or more, requiring Climb checks to get from one surface to the other. Unless a path has been worn and well marked in the floor of a natural cave, it takes 2 squares of movement to enter a square with a natural stone floor, and the DC of Acrobatics checks increases by 5. Running and charging are impossible, except along paths.
Slippery: Water, ice, slime, or blood can make any of the dungeon floors described in this section more treacherous. Slippery floors increase the DC of Acrobatics checks by 5.
Ledge: Ledges allow creatures to walk above some lower area. They often circle around pits, run along underground streams, form balconies around large rooms, or provide a place for archers to stand while firing upon enemies below. Narrow ledges (12 inches wide or less) require those moving along them to make Acrobatics checks. Failure results in the moving character falling off the ledge. Ledges sometimes have railings along the wall. In such a case, characters gain a +5 circumstance bonus on Acrobatics checks to move along the ledge. A character who is next to a railing gains a +2 circumstance bonus on his opposed Strength check to avoid being bull rushed off the edge.
Ledges can also have low walls 2 to 3 feet high along their edges. Such walls provide cover against attackers within 30 feet on the other side of the wall, as long as the target is closer to the low wall than the attacker is.
Stairs
Stairs are the most common means of traveling up and down within a dungeon. A character can move up or down stairs as part of their movement without penalty, but they cannot run on them. Increase the DC of any Acrobatics skill check made on stairs by 4. Some stairs are particularly steep and are treated as difficult terrain.
Trees: The most important terrain element in a forest is the trees, obviously. A creature standing in the same square as a tree gains partial cover, which grants a +2 bonus to Armor Class and a +1 bonus on Reflex saves. The presence of a tree doesn't otherwise affect a creature's fighting space, because it's assumed that the creature is using the tree to its advantage when it can. The trunk of a typical tree has AC 4, hardness 5, and 150 hp. A DC 15 Climb check is sufficient to climb a tree. Medium and dense forests have massive trees as well. These trees take up an entire square and provide cover to anyone behind them. They have AC 3, hardness 5, and 600 hp. Like their smaller counterparts, it takes a DC 15 Climb check to climb them.
Undergrowth: Vines, roots, and short bushes cover much of the ground in a forest. A space covered with light undergrowth costs 2 squares of movement to move into, and provides concealment. Undergrowth increases the DC of Acrobatics and Stealth checks by 2 because the leaves and branches get in the way. Heavy undergrowth costs 4 squares of movement to move into and provides concealment with a 30% miss chance (instead of the usual 20%). It increases the DC of Acrobatics checks by 5. Heavy undergrowth is easy to hide in, granting a +5 circumstance bonus on Stealth checks. Running and charging are impossible. Squares with undergrowth are often clustered together. Undergrowth and trees aren't mutually exclusive; it's common for a 5-foot square to have both a tree and undergrowth.
Forest Canopy: It's common for elves and other forest dwellers to live on raised platforms far above the surface floor. These wooden platforms often have rope bridges between them. To get to the treehouses, characters ascend the trees' branches (Climb DC 15), use rope ladders (Climb DC 0), or take pulley elevators (which can be made to rise a number of feet equal to a Strength check, made each round as a full-round action). Creatures on platforms or branches in a forest canopy are considered to have cover when fighting creatures on the ground, and in medium or dense forests they have concealment as well.
Bogs: If a square is part of a shallow bog, it has deep mud or standing water of about 1 foot in depth. It costs 2 squares of movement to move into a square with a shallow bog, and the DC of Acrobatics checks in such a square increases by 2.
A square that is part of a deep bog has roughly 4 feet of standing water. It costs Medium or larger creatures 4 squares of movement to move into a square with a deep bog, or characters can swim if they wish. Small or smaller creatures must swim to move through a deep bog. Tumbling is impossible in a deep bog.
The water in a deep bog provides cover for Medium or larger creatures. Smaller creatures gain improved cover (+8 bonus to AC, +4 bonus on Reflex saves). Medium or larger creatures can crouch as a move action to gain this improved cover. Creatures with this improved cover take a –10 penalty on attacks against creatures that aren't underwater.
Deep bog squares are usually clustered together and surrounded by an irregular ring of shallow bog squares.
Both shallow and deep bogs increase the DC of Stealth checks by 2.
Hedgerows: Common in moors, hedgerows are tangles of stones, soil, and thorny bushes. Narrow hedgerows function as low walls, and it takes 3 squares of movement to cross them. Wide hedgerows are more than 5 feet tall and take up entire squares. They provide total cover, just as a wall does. It takes 4 squares of movement to move through a square with a wide hedgerow; creatures that succeed on a DC 10 Climb check need only 2 squares of movement to move through the square.
Gradual Slope: This incline isn't steep enough to affect movement, but characters gain a +1 bonus on melee attacks against foes downhill from them.
Steep Slope: Characters moving uphill (to an adjacent square of higher elevation) must spend 2 squares of movement to enter each square of steep slope. Characters running or charging downhill (moving to an adjacent square of lower elevation) must succeed on a DC 10 Acrobatics check upon entering the first steep slope square. Mounted characters make a DC 10 Ride check instead. Characters who fail this check stumble and must end their movement 1d2 × 5 feet later. Characters who fail by 5 or more fall prone in the square where they end their movement. A steep slope increases the DC of Acrobatics checks by 2.
Trench: Often dug before a battle to protect soldiers, a trench functions as a low wall, except that it provides no cover against adjacent foes. It costs 2 squares of movement to leave a trench, but it costs nothing extra to enter one. Creatures outside a trench who make a melee attack against a creature inside the trench gain a +1 bonus on melee attacks because they have higher ground. In farm terrain, trenches are generally irrigation ditches.
Berm: A common defensive structure, a berm is a low, earthen wall that slows movement and provides a measure of cover. Put a berm on the map by drawing two adjacent rows of steep slope (described in Hills Terrain), with the edges of the berm on the downhill side. Thus, a character crossing a 2-square berm will travel uphill for 1 square, then downhill for 1 square. Two square berms provide cover as low walls for anyone standing behind them. Larger berms provide the low wall benefit for anyone standing 1 square downhill from the top of the berm.
Fences: Wooden fences are generally used to contain livestock or impede oncoming soldiers. It costs an extra square of movement to cross a wooden fence. A stone fence provides a measure of cover as well, functioning as low walls. Mounted characters can cross a fence without slowing their movement if they succeed on a DC 15 Ride check. If the check fails, the steed crosses the fence, but the rider falls out of the saddle.
You can read up on weather stuff yourself, but you can hamper the enemy well if weather is used to your advantage. In some cases you can negate ranged attacks almost totally.
