There are many kinds of combat hazards, such as giant bubbles that trap combatants who bump into them, or a narrow band of strong wind that pushes combatants around. GMs often do not have enough variety in their hazard selections. Use these categories to inspire and keep combats fresh.
A classic combat hazard that hearkens back to wargaming days. Use of mixed terrain on the battlemap provides many possible dangers and tactical options.
Sun Tzu wrote about maintaining high ground and using the sun’s reflection on water to blind your foes. Mike Mearls in D&D 4E writes about rock slides and treacherous ice sheets. Past combats in my games have seen cliffs and boiling streams.
How much terrain is covered?
You need to decide when designing and placing terrain how much coverage it has. If the terrain hazard covers the whole battlefield, then everyone is affected. If it doesn’t, only a few are affected.
Partial coverage is more interesting, especially if there are two or three different terrain types, because it offers choices during the combat.
If everyone is affected equally by terrain, there is no choice, and combatants just learn to deal with it. Pockets or zones of terrain create potentially cool offensive and defensive tactics.
Limit terrain to two or three varieties
If you place too many terrain types on the battlefield you’ll slow combat down and over-stimulate encounters. Most of the time consider up to three terrain types for combat:
Where other terrain types are not present on the battlefield the default terrain is in effect.
Default terrain sets player expectations at the start of battle. Whether the terrain is simply dirt, bubbling swamp water, or a field of broken glass, this defines normal for the fight. Any other terrain types will be measured and evaluated against this, which means they need to be more interesting than the default in some way.
For example, if your default terrain is just grassland with no special effects, and you add dirt areas with no special effects, the dirt will be considered boring – if it is considered different terrain by players at all. The additional terrain will have no impact on flavour or gameplay, so why bother?
Avoid terrain inflation – aim for different and interesting most of the time, not more severe. Avoid the trap of escalating terrain effects just to make other terrain interesting. This is important to note because there can be carry-over of player expectations from previous battles, especially if the game has been in a themed region for awhile and encounters share terrain traits. You might be tempted to make each successive encounter’s terrain even wilder and deadlier than the last, which will end badkly for you before long. Instead, try to make terrain different but not more severe.
For example, in the 371st plane of the Abyss, the ground (default terrain) is made entirely of broken glass. Unprotected feet are ripped to shreds within seconds. Falling prone causes extra damage. Falling from a height causes additional wounds if the victim makes it to the ground. During periodic windstorms, victims caught without cover take damage each minute from airborne glass shards. And making camp with a good place to sleep is hell, er, the abyss.
During a battle on this plane you add another terrain type – grassland. Boring old grassland. It might seem like a letdown because grassland has no interesting traits. Yet, to the players, this terrain will seem like a godsend. It’s safe! No extra damage. One can fall prone here all they want.
You might have been tempted to make non-default terrain hot glass, killler thistles made out of glass shards, or glass +1. However, the grasslands is different enough that it offers fun gameplay and combat options without inflating danger levels to an extreme.
So, you don’t always need to beef up default terrain with even more diabolical terrain – it just needs to be different and interesting to the players.
Often you will have a variety of terrain that all blurs together because it doesn’t add much flavour, different game play, or game value. Consider the typical village region battle with grass, cropland, dirt road, and light foliage. Despite having four terrain types, they all play the same.
I would bundle the terrain types up and call them all default terrain, perhaps in this case, village terrain. This gives you room to offer up more interesting terrain as needed.
This is terrain similar to the default but with one or more properties that are different. Enhanced terrain is often a derivative of the default terrain, and so it becomes a thematic as well as a tactical element. It also should generate greater danger or tactical options than the default terrain.
For example, the combat might be in woods. The default terrain is light trees and foliage. The enhanced terrain could be heavy trees and foliage that block movement, break line of sight, and provide cover; a pile of rocks that offers height advantage, cover, and ambush from a small cave; or a stream that blocks tracking and allows more rapid movement.
You might add rain to village terrain to make the road muddy and tricky to maintain footing on, snow to make non-road parts difficult to walk through and fight in, or deep snow to make ambush possible from any location.
This is terrain that is a lot different than your default or enhanced terrain. It can be within theme or breaking it, but it should have notably different game play. It can be extreme, and if so, should be limited to small areas of the battlefield, else it risks being considered default.
Special terrain should increase drama or have the potential for big impact. Perhaps the side that reaches it first, or figures out how to use it to their benefit first, will receive great tactical advantage.
For example, there might be three magic rune circles spread around the battlemap. If people are standing in all three at the same time they receive a significant magical boon that lasts three rounds. This special terrain might change combat from toe-to-toe hacking to positional play with both sides trying to get members into the circles and repelling the other side from doing so at the same time.
Another example might be poison globe plants that allow combatants to search for their fruit, which can be thrown and explode in a burst of poison spores upon impact. You could decide these plants hide well in thistles, so it takes time to find the fruit.
A third example is a combat that takes place near in a small crater. The ground is devoid of plants and the rocks are a strange orange colour. In certain areas larger parts of the celestial body remain intact beneath the ground. These areas have strong magnetism. Anything involving metal, such as moving in metal armour or swinging a sword, meets with great resistance, inflicting combants with potential movement, attack, and defense penalties.
Avoid too much terrain
Earlier I mentioned that offering too many hazards slows combat down and over-stimulates. Multiple terrain types that add a lot of extra rules to an encounter slows combat down because of the additional data tracking and communication involved. Players might get confused, forget, or not pay attention, resulting in lots of extra tabletalk about what terrain type has what effects. This extra data must be dealt with by every player each time it’s their turn. It also creates more for you to think about while game mastering.
If you have a rainbow of terrain types, any dramatic or flavour effects get lost in the crowd. Having magic runes, broken glass, boiling streams, and piles of rocks in every encounter deprives each of these interesting terrains spotlight time. Players will come to expect this large selection each combat, making fights with just two or three terrains seem less exciting.
Also, don’t forget there are several types of hazards. Monopolizing hazards by way of terrain each time is another way to make hazards less interesting over time.
The best case is to stick with two or three terrain types each combat – default plus a combination of one or two enhanced or special terrains. Then, unleash the full menu for important combats, such as with stage bosses or rivals for climatic scenes, or for encounters that have special significance to the PCs.