Gang of Three
The Gang of Three are a trio of NPCs who are residents of Kolima Village, referred to as such by the other citizens because they tend to be seen around each other. They are the subject of a sidequest in Golden Sun that can be permanently missed. One of the three is a young woman whose name is given as Jill; she makes a reappearance in Golden Sun: Dark Dawn in a role that is more directly related to the plot.
In Golden Sun
The Gang of Three are at the Kolima side of Bilibin Barricade, in the midst of attempting to stack themselves on top of each other to reach a tree full of persimmons, when Tret lays a curse on Kolima Village's citizens in a blind rage in retaliation for their lumberjacks taking their axes to him. Like the rest of the citizens in the town proper, the Gang of Three are transformed into inanimate trees that can only communicate in thoughts. If Isaac and his friends pass east through the Barricade before heading in the direction of Mercury Lighthouse, they pass by what comes across as three human-sized trees stacked on top of each other, portending Kolima Village's fate. Isaac's party eventually brings Tret back to his senses by force in Kolima Forest, but he is too weakened to undo the curse, so Isaac's party must travel back west through the Barricade to -- in part -- look for the healing waters of Mercury Lighthouse.
Later, the band of Adepts led by Saturos -- who Isaac's party is pursuing and opposing -- passes east through Bilibin Barricade, and the group pushes the stack of trees down. Jill, in her tree form, is at risk of being swept downstream. Isaac later returns east through the Barricade to pursue Saturos again, and he has an opportunity to use the Move Psynergy to bring Jill to a safe point on the shoreline. If Isaac does not do this, then by the time he uses the healing water to restore Tret and the latter undoes the curse, Jill will be gone for good, leaving her two friends in a mournful daze in which they muse that they will now be the "Gang of Two" for the rest of time. They will vow never to climb on each other's shoulders again.
If Isaac Moves Jill to the shoreline before healing Tret Tree and undoing the curse, on the other hand, all three will return to human form in good health. If Isaac returns to the Bilibin Barricade, the Gang of Three will recognize him and profusely thank him, and Jill will grant a Hard Nut as a token of her appreciation.
Jill makes an appearance thirty years later; while she is unnamed and there is no mention of the other two, her identity is confirmed by what she vocally remembers about her encounter with the Warriors of Vale, who Isaac would controversially lead to unleash the Golden Sun event upon the world. She weathered the tumultuous series of events that subsequently transpired for Kolima Village, wherein both it and Kolima Forest were somehow shifted further to the east so that it was now located just north of the then-tiny hamlet known as Saha. Jill eventually became both the de facto mayor of Kolima Village and the proprietor of a business revolving around the sales of Dream Leaves, which the Dream Tree -- one of the four trees that make up Kolima Village -- was now producing. She would also become a mother of two young boys.
At around the time of Matthew's quest for a Roc Feather in this era, Kolima Village falls victim to another curse, which is brought about by a haunting and vengeful lizard-like entity named Sludge; it represents the wildlife that once lived in the Saha marshes before the Golden Sun displaced Kolima Village and made it occupy the space the marshlands were once based within, driving the marshlands underground and killing many creatures. The curse that Sludge has laid on the Dream Tree corrupts its Dream Leaves so that they cause horrible nightmares, and the removal of the economic viability of the Dream Leaves is a destructive blow to Jill's livelihood.
Matthew's party of Adepts passes through Kolima Village on their way to speak with Tret on some of their own business pertaining to the Mountain Roc, and they meet Jill, who notes their resemblance to the Warriors of Vale who once saved her and her friends from a flooding river. As she explains how she has been waiting decades for the Warriors of Vale to return, she exhibits slight bouts of delirium because of how Sludge has haunted her dreams for a while by this point. Jill confirms that Kolima Forest itself is impassable because of the same curse. Matthew accepts the challenge of taking on the source of the curse, so Jill leads Matthew into the Dream Tree and lets his party ingest corrupted Dream Leaves so that they can engage Sludge on a seemingly dream-like plane. Matthew's party find themselves in the Phantasmal Bog -- which is either the marshlands that were driven underground by the Golden Sun event or a meta-representation of such -- and slay Sludge, ending the active source of the curse.
The Dream Leaves are now providing neutral dreams, and Jill's emotions are now a mixture of gratefulness over Matthew's accomplishment and resignation that his party has done enough for the village. While she goes outside the Dream Tree to tell the other townspeople the news, Matthew suddenly heals the Dream Tree with what turns out to be a vial of Hermes' Water he had received previously, the very water that solved Kolima Village's last problem. This is necessary for Matthew to proceed on his objective to meet Tret.
With the curse dispelled from Kolima Village and quality Dream Leaves in supply again, a great pall is lifted from both Jill and everyone else's temperament. Nonetheless, Jill is rather given to putting down the notion that anyone would want to meet Tret. When asked, she tells Matthew that Tret lives in the center of the forest where she states he cannot be reached anyway, and at the same time she spouts in a self-contradictory fashion that there is no such person as Tret. After a moment of catching herself, Jill asks Matthew to forget this conversation ever happened and states that they have nothing more to talk about. Clearly, the near-death experience she had on account of Tret's curse thirty years ago has colored her perceptions deeply.
Jill's fate during the remainder of Dark Dawn is unknown; Kolima Village gets caught up in the miasma of shadow generated by the Grave Eclipse caused by the machine underneath Belinsk, which causes many darkened monsters to emerge from their haunts and sow a great deal of death across Angara. Ironically, this event comes about in part because Matthew's party gets manipulated by his antagonists, and Tret and his consort Laurel had warned Matthew's side of the dire secrets underneath Belinsk precisely to prevent such an occurrence.