Level Up (レベルアップ, Reberu Appu?), also known as Level Lust, EXP Up, Double EXP, Knowledge to Power, Accrue EXP, Smart Valor, is a support ability, mostly found on pieces of equipment, namely accessories, that usually doubles the amount of experience points a character earns from battles. It is an ability usually acquired around midway to late in the game.
Level Lust is an ability gained from an augment found in the Hummingway Home in the game's Nintendo DS version. It is a support ability that increases the amount of EXP gained from battles by 50%. It can be obtained multiple times via the New Game Plus feature.
Double EXP is an ability found in Growth Egg, which can be equipped by every character. It doubles the amount of experience gained from battle. It can be found inside Darill's Tomb, in a hidden room after completing a puzzle. It can also be obtained from the Coliseum by betting a Tintinnabulum, or morphed from Vasegiatta, Marchosias, and Galypdes.
Level Up is an ability found on the EXP Plus Materia. At Level 1, it increases EXP earned by x1.5, and at Level 2, by double. The EXP Plus Materia can only be obtained after Meteor is summoned at the Gold Saucer's Wonder Square, for 2000 GP. The effect doesn't stack.
Level Up is an ability that can be learned by everyone. It is learned through Iron Helm, Egoist's Armlet, Fairy Earrings, Pearl Rouge, and Rosetta Ring. It increases the experience earned by 1.5, rounded down.
Mastering this ability requires 75 AP for Zidane, 30 AP for Vivi and Dagger, 50 AP for Steiner and Amarant, 40 AP for Freya, 60 AP for Quina, and 65 for Eiko. Seven Magic Stones are needed to equip it.
Though there is no EXP and therefore no EXP multiplier in Final Fantasy X, there are various AP multipliers, including the weapon auto abilities Double and Triple AP, and the Overdrive → AP ability which gives the player AP instead of filling up the Overdrive bar.
The party can double their EXP intake by equipping the Embroidered Tippet accessory. It can be found in a chest in the Babbling Vale of the Mosphoran Highwaste after reaching the Phon Coast, stolen from the Coeurls on Tchita Uplands, or bought from Old Archades for 5,000 gil.
Knowledge to Power is an ability learned by Ashe that increases the amount of EXP gained for the whole party, and is learned from the Embroidered Tippet accessory. How much the accessory increases EXP intake appears to depend on the battlefield.
Accrue EXP is an ability that allows a character to gain EXP as they move. It is learned from the Arithmetician class for 400 JP. EXP Boost, also known as Gained EXP UP, is a support ability learned from the Arithmetician job for 350 JP. A unit with this ability will receive 1.5x the experience from every action they perform.
Smart Valor slightly increases the amount of EXP the user gains from defeating enemies, and can be customized onto equipment through the Extreme Mania jewel.
The three Chocobo accessories Chocobo Down, Chocobo Wing and Chocobo Feather offer 20%, 50% and 100% bonuses to Exp earned in battle. The Growth Egg increases Exp earned by 20%, and the Excalibur II increases earned Exp by 100%.
Three abilities learned at Level 100 convert earned Exp in battle into HP, Bravery or EX Force, depending on the ability. In Dissidia 012, Exp to HP and Exp to Bravery are learned at Level 99, while Exp to EX Force and the new ability Exp to Assist are learned at Level 100.
EXP Up is a special ability with three levels of power, each level increasing the HP earned in battle by 20%. No character learns any version of EXP Up normally, they can only be learned by usage of the EXP Up Scroll items.