Terrain: Most foes try to make some use of the local terrain, even if all they do is hide behind trees. However, the lay of the land determines what is possible during a combat and what’s not. A forest choked with thick undergrowth offers lots of cover and concealment, which generally makes it a good place for ambushes. A forest’s trees and undergrowth also tends to restrict movement—especially mounted movement—and missile fire. Likewise, a group of 10 archers can’t line up shoulder-to-shoulder and deliver a devastating volley if the battle is taking place in a five-foot-wide dungeon corridor.

Terrain is usually beyond the control of the participants, except that magic can alter terrain or appear to alter it. A move earth spell, for example, can allow a commander to create just about any battlefield layout desired. A hallucinatory terrain spell can prompt opponents to do foolish things, such as maneuvering to avoid a marsh that really isn’t there or coming to a halt behind a pile of illusory boulders that appear to offer good cover.

Even without magic, creatures who are prepared for a battle can choose where to fight. The best possible defensive terrain offers the defenders cover while forcing the attacker to approach in the open, preferably to spend a long time exposed to attack before they can attack themselves. Castles are built the way they are to exploit this concept: The cleared area around the castle offers little or no cover. The castle’s moat and walls keep the attackers outside where there is no cover, and the walls provide cover for the defenders.

Smart foes stay alert for opportunities that the terrain creates. The old trick of hiding atop a cliff and rolling boulders down upon hapless travelers below is a good example of this type of tactic. Player actions often create less-obvious opportunities, however. For example, characters who decide to climb to a canyon’s rim—to avoid having rocks dropped on them later—just might find themselves attacked while they literally hang on for dear life.

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