Treyni is a Dryad serving as the primary overseer and protector of the Jura Great Forest. She is the eldest of three sisters, with Trya and Doris as her younger siblings. Her origins trace back over a millennium when she served as a fairy under the Elemental Queen Ramiris. Following Ramiris's significant changes at the end of her lifespan, Treyni and other fairies sought refuge in the Jura Forest. Storm Dragon Veldora granted them permission to reside there; in gratitude, Treyni became the forest's guardian, meting out punishment to threats against its residents. She possesses an ethereal appearance, often described as slightly transparent with light green hair, blue eyes, and distinct green marks beneath her eyes. She typically wears a full-length aqua-colored dress with white sleeves and goes barefoot, emphasizing her connection to nature. Her personality balances dignity and approachability. As the forest overseer, she is diplomatic, intelligent, and skilled at mediating conflicts. She maintains a calm, analytical demeanor when addressing threats. However, around Ramiris—whom she deeply reveres—Treyni reveals a more childish, emotional side, often spoiling Ramiris excessively and causing stress for their assistant, Beretta. Her laidback attitude and tendency to delegate responsibilities have occasionally incited envy in her sisters. A defining quirk is her obsession with potato chips, stemming from Ramiris's joke that dryads are born from potatoes. This manifests comically: she consumes chips during meetings, adds potatoes to meals secretly, recovers energy from them when exhausted, and in the spin-off *The Slime Diaries*, runs a bar called "Snack Jura" but is punished for slacking off by peeling potatoes. Her abilities are deeply tied to the forest. She communicates with plants to gather information, moves instantly through the forest, and can fuse with high-class spirits to amplify her powers. Her physical form is spiritually linked to the Great Sacred Tree (Dryas), limiting her range and duration outside the forest. After Rimuru Tempest awakens as a True Demon Lord, he transfers her spirit into a specialized doll body crafted from the Sacred Tree. This upgrade eliminates her distance restrictions and enhances her magical and spiritual capabilities, allowing her to operate freely beyond the forest—most notably in managing the Dungeon's control room alongside her sisters. Her relationship with Rimuru begins when she seeks his aid against the Orc Lord crisis. Recognizing his potential, she nominates him to lead the Jura Forest Alliance, securing the allegiance of dryads and treants. After Ramiris relocates to Rimuru's nation, Treyni and her sisters follow, becoming integral to Tempest's operations. She assists in urban planning to harmonize Rimuru City with nature and later co-develops traps and systems within the Dungeon. Treyni also demonstrates combat prowess, confronting antagonists like Laplace and Zarario. Her character evolves from a secluded guardian to an active participant in Tempest's societal and technological advancements, maintaining her blend of wisdom and whimsy.