Resistance

Resistance is a battle statistic that determines how much damage an Adept or enemy takes from element-based attacks. An Adept will have the most resistance to their innate element, and have lesser resistance to the other three elements. An Adept with no Djinn set and no resist-increasing items equipped will have 114 resist in their innate element, 88 resist in their neutral element (Mercury-Venus and Jupiter-Mars), 87 resist in their opposed element (Mercury-Mars and Jupiter-Venus), and 86 resist in their symbiotic element (Mercury-Jupiter and Venus-Mars). As with Elemental Power, resistance works as a percentage multiplier on Element-based attacks (such as Psynergy), except that the damage dealt is inversely proportional to the Resistance. For example, if an enemy casts a Psynergy-based attack that is described as dealing 200 damage and the targeted Adept has 77 Resistance, then the attack will deal approximately (200 damage)(100/77) ~= 260 damage. The exact final amount is changed by a small, random amount. Thus, a resistance of 200 will cause the Adept to take half the damage they would take if they had 100 Resistance (i.e. the "usual" damage).

Temporary increases

 * Using a Psynergy from the Ward Psynergy series or Magic Shell Psynergy series.
 * The Djinn Breeze, Steam, or Mellow.
 * Using an item in battle: Aura Gloves, Fireman's Pole, and Golden Ring

Permanent increases

 * Set a Djinn. It will raise the resist of the Adept by 5 in that element, regardless of class.
 * Equip resistance-increasing equipment. A full list of equipment which affects resistance to each of the four elements can be found here for Mercury, here for Venus, here for Mars, and here for Jupiter.

Temporary decreases

 * The Weaken Psynergy series.
 * The Mercury Djinn Sour, Claw, and Pincer.
 * The Unleash effects of several weapons: Corsair's Edge, Mighty Axe, and Ninja Blade.
 * Also it should be noted that the Break Psynergy will remove the effects of any temporary increase.

Permanent decreases
Only two are known: equipping the Demon Mail or Stealth Armor.