World effects involve effects upon the natural world over and above what a natural man could be expected to perform. Generally none of these skills would be available in universes without magic, technology akin to magic, supernatural elements, or superhuman powers, so taking any of these skills would be per the GMs judgment.

Although these powers may be used as attacks in many cases, they aren't generally used simply as mechanisms for damaging an opponent. Instead they are ways of subverting natural laws and the laws of physics to better deal with the dangers of the world and accomplish the purposes of a particular campaign.

Gusts of wind, forcing breathable air into otherwise unbreathable places, turning away projectiles, pushing away poisonous and disease-ridden vapors, and using the air to fly are among the powers of air manipulation. Each effect takes an action and holding an effect already initiated takes a passive action.

Generally the effects of air manipulation don’t cause damage directly but that doesn't mean that damage cannot be caused at all by the use of air. Knocking someone off a cliff or sending something dangerous flying at an opponent can most definitely cause damage.

When used for flying, normally special clothing for catching the wind is required. And the amount of wind required is usually enough to let everyone know that someone manipulating the air is present, so stealth is usually fairly impossible to accomplish.

When used to turn away projectiles, only slower projectiles such as arrows, bolts, and darts are affected. Bullets generally aren't unless they're shot from very long distance, and even then an area of effect would likely be required to modify it's trajectory enough to miss. When used against appropriate projectiles, a defensive action can be used and the missile is considered to have missed.

When combined with the summoning ability, air elementals can be summoned.

Moving earth around, detecting things within nearby earth, forming earth into usable weapons, tools, armor, or other items are among the powers of earth manipulation. It should go without saying that earth must exist nearby for this to be effective. Each effect takes an action and holding an effect already initiated takes a passive action.

The effects of earth manipulation may cause bludgeoning or piercing damage if used as an attack with damage calculated as a standard damage roll.

If used as protection using a defensive action, earth offers standard defense dice vs piercing, slashing, bludgeoning, burning/acid, freezing, and electrical attacks.

When combined with the summoning ability, earth elementals can be summoned.

Moving fire from one place to another and increasing or decreasing the strength of a fire are among the powers of fire manipulations. It should go without saying that fire must exist nearby for this to be effective. Each effect takes an action and holding an effect already initiated takes a passive action.

Although this could be mistaken for the burning skill, it isn't really that. The effects of fire manipulation can cause burning damage with a standard damage roll, but whereas burning is more the ability to generate searing and damaging heat out of nothing to a point where items can spontaneously combust, fire manipulation is more the ability to use existing fire to do whatever needs to be done.

When combined with the summoning ability, fire elementals can be summoned.

Water-breathing, manipulating water, purifying water, using water against fire and earth elements are among the powers of water manipulation. It should go without saying that water must exist nearby for this to be effective. Each effect takes an action and holding an effect already initiated takes a passive action.

The effects of water manipulation are unlikely to cause much damage unless they are used to float obstacles at an opponent, but that isn't to say that the water manipulator is powerless against opponents. Water can be used to blind, slow, and even drown opponents if used properly.

When combined with the summoning ability, water elementals can be summoned as can fresh, drinkable water.