Luff

Luff is a Jupiter Djinni found in Golden Sun and Golden Sun:  The Lost Age.

Luff is the seventh and final Jupiter Djinni in the original Golden Sun, and can also be  acquired in Golden   Sun: The  Lost Age. Although it is not the party's seventh Jupiter Djinni in The Lost Age, Luff is still ordered as the seventh Jupiter Djinni when  equipped to characters. Because it is not available until after most other Jupiter Djinn can be found, however, the separate Djinn list  viewable with the Select button from the status screen lists Luff and  all other Jupiter Djinn from Golden Sun after all of the Djinn introduced in The Lost Age. According to this order, Luff is the eighteenth and final Jupiter Djinni in The Lost Age rather than the seventh, but this order has no influence elsewhere in the game.

Basic description

 * "Seal a foe's Psynergy."

When Set, Luff increases its Adept's base HP by 11, base Psynergy Points by 5, base Defense by 2, and base Luck by 1.

When Luff is unleashed in battle, the target is afflicted with the Psynergy Seal status condition, which prevents it from using Psynergy (i.e. an effect that would consume PP), just like the Bind Psynergy. Unlike the Bind Psynergy, which has very iffy accuracy, Luff is guaranteed to inflict Seal on the enemy it is used on.

In Golden Sun and The  Lost Age, Luff's unleash animation visually resembles  the user summoning the purple image of a Jupiter Djinni above the target, and then the same visual as the Bind Psynergy - a purple, glowing, holographic image of a triangle spins around the target and shrinks into it, and inflicts the Psynergy Seal symbol.

Locations
Golden  Sun: Luff is located in Babi Lighthouse, in a lone platform in the center  of a large abyss where it appears unreachable. To get to it, in the screen outside the main building with all the wounded workers, climb  down the ladder to the left, use Move to move the left pillar in the  underground one space left, climb back up, climb down the ladder  underneath the pillar to the right, use Move to move the right pillar  one space left, make your way up to back outside where a small plant is  visible, cast Growth on the plant, climb up and slide down to the  elevated entrance into the building, and slide down the one slide of  three you're able to reach in the room you immediately appear in. You will drop down to Luff's position. Save your game, then attempt to acquire it through battle.

Golden Sun: The Lost  Age: Players must transfer data from Golden Sun to The Lost Age in  order for Luff to be acquired at all, because if they don't, Luff will  not be among the Djinn Isaac's party has with them when they join forces  with Felix's party late in the game, and the "make-up" Jupiter Djinni at SW Atteka Islet will be the other missing Jupiter Djinni from the first game, Squall.

As an opponent (Golden Sun)
Statistically, Luff has 688 HP, 62 PP, 302 Attack, 85 Defense, 177 Agility, and 21 Luck. Like all other Jupiter Djinn that are fought, in terms of resistance, it has a Jupiter Resistance rating of 193, Mercury and Mars Resistance ratings of 100 each, and a Venus Resistance rating of 25, and in regards to its abilities it uses its available Jupiter-based attacks with a Jupiter power rating of 125.

Luff can use the following battle commands:
 * Wind Slash: Used 53 out of 256 times, this is a Psynergy spell that shoots out a moderately large purple air swath at each Adept, dealing a Jupiter-based attack with a power rating of 50 and a range of 3. This ability consumes 9 of its user's PP.
 * Tornado: Used 47 out of 256 times, this is a Psynergy spell that causes two whirlwinds laced with electric charges to spin through the party, dealing a Jupiter-based attack with a power rating of 80 and a range of 5. This ability consumes 14 of its user's PP.
 * Blue Bolt: Used 41 out of 256 times, this is a Psynergy spell that causes two thick purple lightning bolts to strike at the party, dealing a Jupiter-based attack with a power rating of 90 and a range of 3. This ability consumes 14 of its user's PP.
 * Shine Plasma: Used 35 out of 256 times, this is a Psynergy spell that causes a three large bolt of purplish lightning bolts to strike at the party, dealing a Jupiter-based attack with a power rating of 100 and a range of 5. This ability consumes 18 of its user's PP.
 * Destruct Ray: Used 29 out of 256 times, this is a Psynergy spell that causes an array of thick purple lightning bolts to thoroughly assault the party, dealing a Jupiter-based attack with a power rating of 150 and a range of 3. This ability consumes 21 of its user's PP.
 * Attack: Used 28 out of 256 times, this is this monster's standard physical attack, but for this monster it is counted as a Jupiter-based attack rather than a non-elemental attack.
 * Flee: Used 23 out of 256 times, this enemy has the ability to attempt to Flee the battle, thereby ending the battle if successful without rewarding you with the associated EXP, Coins, and the Djinni itself.

When defeated it yields 677 EXP and 506 coins and the Luff Djinni is added to your party's Djinn collection. If you fell it with an offensive Venus Djinni like Flint, its rewards increase to 880 EXP and 657 Coins.

Even though this is the last fought Djinni in the game, and thus should be very easy to blow away with full-powered summons in one turn, the amount of effort spent getting here demands that you save your game before attempting to get it, lest it happens to flee.

Analysis
General: Luff and any of the Djinn identical to it - Rime in The Lost Age and Dark Dawn, and the Mars Djinni Brand in Dark Dawn - automatically make the Bind Psynergy worthless because they inflict the status effect with full accuracy, compared to how often Bind misses. There are only specific cases in any game when this effect can be useful, though, since it only prevents an enemy from using Psynergy - any ability that uses up any PP from the user's PP meter - while not limiting its ability to attack and use Monster Skills.

By game
Golden Sun: Luff is the one Djinni in this game filling the role of a fully accurate version of Bind. Easily the greatest example of this being useful is in the Deadbeard boss fight, because every one of Deadbeard's battle commands that is not its physical attack is a  Psynergy spell that either deals mass damage or buffs himself. The Psynergy seal typically lasts two turns, so the Adept that has Luff (preferably Ivan as he is meant more as a supporting Adept anyway and  can easily have the necessary higher agility rating than Deadbeard) can  use it on the first turn, then Set it back on the second turn, and  repeat ad infinitum so that the other three Adepts can battle Deadbeard  safely throughout the whole battle while Deadbeard can only launch  un-bolstered whacks.

Golden  Sun: The  Lost Age: When Isaac's party joins Felix's party along with their returning Djinn  (granted that Password data transfer is in effect), Luff's effect  makes it a second Rime, a Mercury Djinni found later in the game in  Ancient Lemuria. However, enemies with Psynergy abilities that would be worth using Luff/Rime on to limit their options meaningfully remain few, and none of these are as adversely affected by the seal as Deadbeard from the previous game. However, it can neutralize some of the bigger Flame  Dragon's powerful psynergies - Meteor Blow and Rising Dragon, namely. In addition, Sentinel would only be able to use his physical attack and Armor  Crush; while a powerful single-target attack on its own, the effect of Armor Crush can be easily fixed with the defense-boosting Iron and  Corona, and Sentinel would be unable to use the Break Psynergy to remove these buffs off your party because that would be sealed. However, there are many ways where using one of these on an enemy would be the opposite of beneficial; on Dullahan, for example,  you'd be preventing him from using his comparatively harmless Psynergy  spells and forcing him to only use his extremely powerful monster skills  like Formina Sage and the summon Charon.

Name Origin
A luff is the vertical edge of a sail that is closest to the direction of the wind, which associates with the Jupiter element.