When Set, Dewdrop increases base HP by 8, base Psynergy Points by 4, and base Attack by 3.
When Dewdrop is unleashed in battle, all status ailments on each currently active party member that is not Downed are removed. This includes the conditions that would disappear at the end of each battle, including Stun, Delusion, Sleep, Psynergy Seals and Death Curse, and permanent conditions that would have to be removed manually, including Poison, Venom, and Haunt.
In Dark Dawn, Dewdrop's unleash animation visually resembles the user summoning the 3D model of Dewdrop above the party in a particularly large and glitter-spreading light blue flash. This glitter floats down through the party's area as Dewdrop floats above the party.
Golden Sun: Dark Dawn: Dewdrop is visible on its own island in the first, snow-covered screen you enter when you go to Teppe Ruins north of Te Rya Village. Before you can get it, however, you need to purchase the Trusty Staff from the artifacts section of the female shopkeeper in Te Rya Village. Then, when you enter the screen and see Dewdrop, cast the Fireball Psynergy on it to make it dive into the water. Then go into the tiny cabin to the left and talk to the male NPC in front of the fireplace, and give him the Trusty Staff. Follow him outside to the right, and in a short cutscene the NPC will fish up Dewdrop for you. You collect it right away. Teppe Ruins is permanently closed off along with the rest of the locations in the Morgal region later in the game, so Dewdrop can be permanently missed once you enter the final gate in the depths of Belinsk Ruins.
General: The effect of curing all status ailments, let alone on all currently active Adepts in the battle, is exclusive to Djinn like Dewdrop. In one maneuver, it removes from across the entire battling party all occurrences of the status conditions that the Elixir item and Restore Psynergy remove off a single targeted ally (Sleep, Stun, Delusion, Psynergy Seal, and Death Curse), the damaging status conditions that the Antidote item and Cure Poison Psynergy remove off a single targeted ally (Poison and Venom), and the Haunt status condition that can otherwise only be removed either by the afflicted ally being Downed or by paying at a Sanctum. This makes Djinn like Dewdrop conceptually invaluable, though there seem to be few real combat situations where such a healing effect can truly be worth it - temporary status conditions are not extremely dangerous because battles go by fast anyway and they remove themselves once the battle is over, and when anyone is poisoned during a battle, it is typical to win the battle quickly, and then use Cure Poison on each poisoned Adept in the field. The Haunt condition does not even apply itself much to be of real worry in general as well. Effects like Dewdrop are most useful in particular boss encounters when various status conditions are spread around a lot, particularly if you are setting up for a Mercury summon in that battle. Identical equivalents to this Djinni in the Game Boy Advance games are the Mercury Djinni Tonic and the Venus Djinni Salt.
Golden Sun: Dark Dawn: Dewdrop is the first of the two Djinn providing this specific status-healing effect in this game; the second is the Venus Djinni Clover gotten much later in the game when Himi joins the party. While this causes Dewdrop to have more opportunity to be used than Clover, perhaps the only fight that gives these Djinn real opportunity to be useful is against the Ancient Devil at the endgame. This enemy can summon Haures, which potentially afflicts multiple Adepts with the damaging and threatening Venom status condition. The enemy can also inflict Death Curse on single targets, and a boss battle such as this can last long enough that the instant death effect can actually take hold. All occurrences of both of these status conditions can be removed at once by using Dewdrop and/or Clover, and may mean the difference between victory and defeat.