Treyni

The eldest of the three Dryad sisters. The second sister is Trya (voiced by Kana Asumi), and the youngest is Doris (voiced by Kaori Maeda). She appears as a mysteriously beautiful woman with a slightly translucent appearance. When Ramiris fell to become a fairy, they also transformed from spirits to fairies, and after being separated from Ramiris, they were protected by Veldora and entrusted with the management of the Great Jura Forest. In Volume 2 of the books, she informs Rimuru of the armed uprising by the Orc Lord Geld, and after resolving the incident, she nominates Rimuru as the chairman of the Jura Forest Grand Alliance, pledging loyalty to Rimuru along with the Treants. With Ramiris's relocation to the Federation of the Magic Kingdom, the Dryads also move to the labyrinth and officially become subordinates of Ramiris with Rimuru's permission.

She is a reliable person but is overly indulgent only towards the revered Ramiris. In the forest, she boasts overwhelming strength, capable of instant teleportation and information sharing through plants, and enhancing her abilities by merging with higher spirits. She can operate as an avatar, but since her main body is in the Great Spirit Tree (Dryas), her time is limited. In Volume 6, by Rimuru's hand, her spirit is transferred to a spirit magic core and housed in a puppet made from the Great Spirit Tree, evolving into a Spirit Tree Puppet Fairy with enhanced abilities and freed from her constraints. In the labyrinth, while the Dryads serve as control room operators, Treyni also excels in combat, having fought twice against Laplace and also battled Zarario.