Magic damage is almost always associated with an element.
Non-elemental damage is equivalent to force/sonic damage and nothing can be weak or resist it nor can you swap to it if an ability or class feature would allow you to swap elements. Non-elemental does not ignore hardness and is treated as an energy source.
Physical damage is done by weapons unless otherwise noted.
The general rule of the elements is this:
Wind is strong against earth, which is strong against lightning, which is strong against water, which is strong against fire, which is strong against ice, which is strong against wind.
Wind is weak to ice, which is weak to fire, which is weak to water, which is weak to lightning, which is weak to earth, which is weak to wind.
Shadow and holy are both strong against each other and weak to each other.
See the image above for a better understanding.
Weakness
If a creature is struck by elemental damage of an element it is weak to, it takes 1.5x the normal damage. When a spell of the appropriate element is cast upon the creature and forces a saving throw, the creature suffers a -2 penalty on the saving throw. A spellcaster casting a spell of an element that a creature with spell resistance is weak to, he gets a +2 bonus on his caster level check. Weakness is a damage multiplier, and is added rather than multiplied to other modifiers. A 2x critical against a creature weak to an element deals 2.5x the damage.
Strong
If a creature is struck by elemental damage it is strong against, it instead halves the damage (rounded down, minimum 1). Creatures get a +2 bonus to saving throws against spells of an element they are strong against. Strong is a damage multiplier, and is added rather than multiplied to other modifiers. A 2x critical against a creature strong against an element deals 1.5x the damage.
If a creature is both resistant to and strong against the same element, apply resistance first (20 fire minus 3 resistance then halved for 8).
Format:
Resistance fire 50%, Ice 5+50%
Immunity
Some creatures are immune to specific elements. All spells of the chosen element have no effect whatsoever on a creature immune to that element.
Absorption
Some creatures are healed by damage of a particular element. For example, the undead are healed by shadow damage. In this case, they are immune to non-damaging effects of spells of the appropriate element, and are instead healed when a spell of the element would normally deal damage (for an equal amount). If a creature has absorption to an element disregard any resistance to the same element.
Elemental Resistance
Different from spell resistance, elemental resistance reduces damage by the number and element the creature has. For example, if a creature with 5 Elemental (Fire) resistance was struck by a Fire II spell for 8 points of fire damage, the creature would only take 3 points of fire damage. Multiple sources of elemental resistance do not stack for the same element, if you had Fire 5 from your race but gained Fire 10 from a spell you only count the highest value which would be Fire 10.
If a creature has elemental resistance (all) then apply the reduction to all elements. If class features note all, it typically does not count holy and shadow, and normally lists the allowed elements. This can not apply to non-elemental damage, as it is not an element.
Pathfinder Energy Conversions
Consult the following table should you need to convert Pathfinder energy types into FFd20 elemental types:
Table: Pathfinder Energy Conversions
| Pathfinder Energy | FFd20 Elemental |
|---|---|
| Acid | Earth |
| Cold | Ice |
| Electricity | Lightning |
| Fire | Fire |
| Force | Non-Elemental |
| Sonic | Non-Elemental |