When Wisp is unleashed in battle, the PP meters of all current battling Adepts are restored by 10% of their respective maximum PP meters.
In Dark Dawn, Wisp's unleash animation visually resembles the user summoning the 3D model of Wisp above him or herself, before disappearing quickly in a purple flash. Then, lavender sparkles gather into each Adept from above in order.
Golden Sun: Dark Dawn: Wisp is inside Saha Cistern, the subterranean path that connects Saha Town with Kolima Village, but can only be reached after clearing Phantasmal Bog, defeating Sludge, and acquiring the Crush Tusk. When you are done with that, return to Saha Town, and jump down its left well into the leftmost screen of the cistern where Wisp is up on an elevated platform. Stand below the turquoise rock right of Wisp and cast Move to remotely move it one space right. Climb back out into Saha Town, then jump down the right well. In the screen of the cistern you climb down to, enter the door to your left, and you will find your way west blocked by a brown boulder; use your newfound Crush Psynergy to shatter this rock, so you can proceed left to where Wisp is. It is gotten without a fight. Since Saha and its cistern are part of the Morgal region that get locked off to the player starting late in the game, Wisp can be permanently missed once the final gate in the depths of Belinsk Ruins are passed through.
General: Wisp is a rare effect that heals a little bit of the whole party's PP meters. While 10% of all Adepts' PP meters is small for the most part, Wisp is superior over other Djinn that have the same effect but only restore 7% of all Adepts' PP meters. It can basically be thought of as the multi-target counterpart to the single-target PP-restoring Djinni Ether the same way the Wish Psynergy series is the party-HP-restoring counterpart to the Ply Psynergy series. Because it heals by a percentage, Wisp's PP-healing values get higher as the party levels up, restoring around 30 PP to each Adept that has 300 PP. If only one Adept is out of PP and needs PP to function, though, then Ether is the superior choice. In The Lost Age, the identical counterpart to Wisp is the Jupiter Djinni Aroma.
Golden Sun: Dark Dawn: Wisp can be valuable to have as a means to restore the lacking PP meters of the party. Wisp can be unleashed during a random battle or two to help the whole party's PP meters somewhat if the party is deep in a large dungeon without any Psynergy Stone nearby. It is probably unlikely there will be a situation where this will be a needed support move in the middle of a boss battle, though. This is especially true if the party is wearing equipment that restores PP at the end of each turn. However, it obsoletes the Mars Djinni Flare, which restores even less to the whole party's PP (7%), and yet is found very late in the game.